1. Scientific Humanism

Kepler and Galileo were not philosophers, but natural seientists who lived at a time when natural science was only aborning. What has become for us a stupendous and fateful reality was for them hardly more than a prospect, albeit the prospect of a grandiose venture unlike anything else in the history of man. It was to be a venture of discovery and conquest. Nature, like a vast new continent, lay spread out before them, abounding in riches to be had for the taking. Mathematics was to be the instrument of seizure. With this mighty weapon, itself but newly forged, the whole domain was to be explored and exploited for the benefit of all. Such in brief was the exhilarating prospect, known as “scientific humanism,” which fired the authors of natural inquiry and ushered in the new era that was to follow.

Today scientific humanism seems to be hardly more than a memory. Promise has given way to fulfillment, and with fulfillment has come a sobering sense of reality, touched of late with a grimness which the founding fathers did not anticipate. With its many blessings the grand venture has also brought latterly the hideous threat of extinction. The threat expresses nothing inherent in the undertaking itself, rather a failure in its execution. The spoils of conquest were not shared by all, but reserved for a privileged few; arbitrary rules of eligibility were imposed—religious, political, economic—-in violation of the spirit of the venture. Like a prophet of old, Karl Marx denounced this injustice and called down on our generation the wrath of the wronged. In world Communism these wronged have raised their fists and voices in a raucous demand for their share of the bounty. Slowly, painfully this latter-day “scourge of God” seems to be compelling our grudging compliance with the aforesaid spirit which gave to the undertaking from the outset its profoundly “humanistic” character of being for the benefit of all mankind.

On this understanding natural science is not inherently indifferent to human values; it is inherently relevant. It is not solely a method of natural inquiry, a vast accumulation of natural knowledge. It is also an attitude and way of life, a way of looking at the world and living in the world, an attitude which sets a supreme value on this life and its mundane course—for all.

Natural science was originally so conceived by its authors, and as so conceived has come to engage the minds and efforts of men and nations. Only where it is so conceived, that is, only where scientific humanism prevails, overtly or covertly, can natural science flourish. This is to say that scientific humanism is still the presiding aegis of natural science and must thrive to sustain its offspring. If this be so, then scientific humanism must be more than a lingering memory; it must be as real and present for us as it was for Galileo and Kepler. With its novelty worn off it must have gone underground, there to obtain, like the theory of sensation and monadism, as a “fundamental assumption.”

But it is a unique kind of “assumption”; it is too wide and deep to be encased in a philosophic formula or article of belief. It is not a part of a framework, but a whole framework itself, a pervasive attitude, a comprehensive outlook, appealing as much to the emotions and the will as to the intellect. Let us note briefly some features of this attitude and its characteristic sense of value.

First, and perhaps most obviously, natural science is unique among the endeavors of man in the quality of its cooperation, in calling equally for individual and collective effort. In no other endeavor is there such a complete accord between individual accomplishment and group aggrandizement; in every instance a gain for one is a gain for all, and conversely. Also, in no other group are the admission requirements so general, so free from bias, so universal. Without regard to color, sex, creed, social status or political affiliation anyone may participate to the extent of his talents and training. “In no other endeavor have men with varied abilities, temperaments, and allegiances, cooperated so broadly, so persistently, or so successfully. Nowhere have the values of industry, honesty, imagination, self-criticism, and freedom from prejudice, been more brilliandy demonstrated.” (Dorion Cairns in an unpublished paper.) Never have men so thoroughly cooperated; never have their labors been so richly rewarded—for the benefit of all. In this respect modern natural science is unique, without compare, among the endeavors of men.

To be or become all this, natural science did not require, like an office building, to be preceded by a detailed blueprint of itself. It grew, rather, like a living thing, animated by scientific humanism. Not being the architect of natural science, but rather its elan vital, scientific humanism did not offer itself or its program as a philosophy, still less as a theology, and hence did not seek expression in the form of a doctrine. Without bible or textbook, scientific humanism came to utterance and propagated itself more by deeds than by words. Such words as it did employ—and it was movingly articulate—were chiefly incitements and guides to action. The action contemplated had a single end: the conquest of nature for the benefit of all.

The conquest of nature! Never before had such a notion taken hold in the western world. It was no article of the Christian faith and no tenet of classical philosophy. For the Christian the world was but the dark anteroom to salvation, and for the Greek an object to be known, without thought of mastery. Only the ancient Hebrews had entertained the thought of mastery. And they propounded it seriously. For them it was the very first of the divine commandments. No sooner had God created human beings, than He blessed them and said unto them, “Be fruitful, and multiply, and replenish the earth, and subdue it” (Gen., 1:28). The injunction is repeated after the flood (Gen., 9). And it moves the Psalmist to the most amazing outburst. When he cries “What is man, that thou art mindful of him?” it is not from a humbling sense of man’s inconsequence, but from an exalted sense of his near divinity. “For thou hast made him a little lower than God [Elohim, hence not “angels” as the King James version modestly but incorrectly renders it] and hast crowned him with glory and honor. Thou madest him to have dominion over the works of thy hands; thou hast put all things under his feet” (Ps., 8:4-6). For sheer boldness of conception and utterance I know of nothing to match these words. They are startling even today. And what a glow they add to the prosaic talk of “prediction and control”! Note also that this mandate of dominion was issued to man as man, that it was in his capacity as a human being—not as Jew or Gentile—that he was “divinely elected” to the exalted office of master of creation. Scientific humanism could hardly aspire to a higher sanction—or point up more forcibly the neglect of the first of all the divine commandments.

Even newer in this vision was the idea that mathematics was to be the instrument of dominion. The Pythagoreans had regarded mathematics as a key to a kind of speculative understanding of nature and had deigned to apply it to such phenomena as the motions of the planets and the concordant intervals in music, giving rise to astronomy and harmony. But they eschewed the notion of a general application of mathematics to natural phenomena, especially if it bore any prospect of being useful; this was for shopkeepers, not philosophers. This disdain is well expressed by Plutarch in his life of the Roman general, Marcellus, who captured Syracuse. Archimedes, Plutarch tells us, had contrived some machines “not as matters of any importance, but as mere amusements in geometry”—at the urging of his kinsman, King Hiero of Syracuse. After a vivid account of the effectiveness of these machines in repulsing Marcellus’s assaults by land and water, Plutarch adds, “Yet Archimedes possessed so high a spirit, so profound a soul, and such treasures of scientific knowledge, that though these inventions had now obtained him the renown of more than human sagacity, he yet would not deign to leave behind him any commentary or writing on such subjects; but, repudiating as sordid and ignoble the whole trade of engineering, and every sort of art that lends itself to mere use and profit, he placed his whole affection and ambition in those purer speculations where there can be no reference to the vulgar needs of life.”

Compare this with Bacon’s roughly parallel remarks in the Preface to his Instaurati() Magna. Man is so completely encompassed by nature that “what he does and what he knows is only what he has observed of nature’s order in fact or in thought; beyond this he knows nothing and can do nothing. For the chain of causes cannot by any force be loosed or broken, nor can nature be commanded except by being obeyed. And so those twin objects, human knowledge and human power, do really meet in one; and it is from ignorance of causes that operation fails” (Bacon’s italics).

The tremendous change which has come over the thinking of men could hardly be more dramatically put than by these two aristocrats of their respective cultures. For the one, knowledge is pure theoria, contemplation, in lofty detachment. For the other, knowledge is power of operation in close application to the vulgar facts of life. It makes no difference that Bacon failed to recognize the role of mathematics in the new knowledge of nature. He saw clearly what the new knowledge was aiming at and spoke for all when he stressed its practicality.

New, too, and finally, was the idea that the “fruits,’’ as Bacon called them, of this new knowledge were to benefit all mankind, to mend the fabric of man’s earthly existence. In the same Preface Bacon insists that “the matter in hand is no mere felicity of speculation, but the real business and fortunes of the human race, and all power of operation.” In his New Atlantis he pictures vividly the promised “relief of man’s estate,” the mitigating of human sufferings and the multiplying of human comforts—for all, here and now.

The emphasis in this humanistic vision is unmistakably universalistic and secular, and just as unmistakably a reproof to the old order. The classical Greek ideal, with its lofty speculations for the leisured few, had no room for all mankind. And the Christian, meditating on life eternal, could take but little thought for the secular. Such thought as he did take was largely negative. For to the extent that salvation required forsaking “the world, the flesh, and the devil,” the Christian attitude toward the secular was bound to be one of studied disengagement and neglect; to the extent that it fixed on the depravity of man, the Church could become the portal of salvation only by becoming the escape hatch from the world. In advocating flight rather than dominion, the Christian tradition virtually renounced the world as the tragic scene of man’s fal! from grace, and remanded it to the devil.

Against this denigration of the secular a massive protest was gathering in the minds and hearts of men. Had this protest been more articulate it would have entered the theological battles of the time and engaged both contending parties, Catholic and Protestant alike. Against both it would have inveighed that the negative Christian attitude toward creation was tantamount to 1) damning as evil what the Creator in the process of creating had six times found “good,” the seventh time “very good,” and 2) violating flagrantly the first commandment to “be fruitful and multiply, and replenish the earth, and subdue it.”

But the protest was not thus articulate; it did not press directly for doctrinal formulation, not even for Scriptural vindication. Being a vast transvaluation it spread more by infection than by argument and broke out not so much in opposition to salvation and the Church as in favor of dominion and natural inquiry. This was as it should be, for the new attitude was not primarily negative and protestant, but positive and affirmative of values long neglected. Thus with its syndromes of secularism and universalism, the new attitude found what expression it needed in the call to dominion under the banner of scientific humanism—a call to the greatest and noblest of crusades.

The point of this divigation is that scientific humanism was not in the first instance a philosophy, but a whole new outlook on life and nature and a new program of living by conquest. It was a call, therefore, not to words but to action. As Bacon put it, the matter in hand was “not an opinion to be held, but a work to be done,” a work of unprecedented magnitude calling for an unprecedented effort on the part of men individually and collectively. The call obviously cut across religious, theological, philosophical, national lines, across all lines in fact that divide men from one another. Without regard to their divergent beliefs and loyalties men everywhere were now invited to share in a mighty enterprise from which all could profit.

It was while engaged in this enterprise that Kepler the Protestant and Galileo the Catholic drew their celebrated distinction between primary and secondary qualities. For them the distinction was not philosophical and theoretical, but scientific and practical, a device for facilitating the application of mathematics to natural phenomena. Thus in spite of its philosophic implications—and for us they are many—the distinction remained for these authors of natural science essentially an obiter dictum, a means of clearing away obstructions and getting along with the work in hand. They were content, therefore, to leave to others the controversial task of elaborating its philsophic import.

2. Kepler

Kepler’s version of the distinction turns on the notions of quantity and quality, the first two of Aristotle’s categories of accident. Kepler contrasts his own view with that of Aristotle. Aristotle, he says, tended to regard the qualitative accidents of things as the more fundamental, whereas he, Kepler, regards the quantitative as the more fundamental. The quantitative determinations of things are prior to the qualitative in two respects. They are prior 1) in things and 2) in knowledge. They are prior in things in that they underlie the sensible qualities; they are the underlying, nonsensible elements of order, regularity, “harmony,” such as he found, for example, in optics, music, and mechanics. Of this wonderful and pervasive “harmony of the world” (harmonices mundi) the sensible qualities are only signs or indices, mere effects which only half reveal their causes. The quantitative accidents are prior in knowledge because they are the proper objects of mind. “Just as the eye was made to see colors, and the ear to hear sounds, so the human mind was made to understand, not whatever you please, but quantity.”* This is attested by the fact that mathematics, the most illustrious product of the human mind, is the great discipline of quantity in general. It is by mathematics, therefore, that the hidden harmony of the cosmos in all its quantitative variations is to be discovered and understood.

This dual priority of the quantitative over the qualitative and the marvelous conformity of the human mind to the mathematical nature of things are for Kepler manifest evidences of divine providence. Kepler’s religious fervor verged on the extreme. He was intensely aware of the world as the handiwork of God; and he could have said a resounding “amen” to Galileo’s contention that God’s primary revelation lay in the great mathematical book of nature. Although he was a Protestant, Kepler was not deeply concerned with the reform of the Church or with refinements of doctrine. His concern was with the reform of our natural knowledge and with the refinements of natural inquiry. In this concern he spoke a common language with his Catholic contemporaries and could count on their ready assent to his own proclamations that God created the world in accordance with mathematical harmonies, that He ever geometrizes, that in making man in His own image God so designed the human mind that it should know primařily quantity.

There is philosophy in this, and metaphysics and theology and religion. But it is a mosaic of utterances almost without texture, without regard for the niceties of formulation and consistency. It is but a backdrop to the central action: the application of mathematics to natural phenomena. And since Kepler’s heart was set on this central action he was content to leave the backdrop as it was. He was a natural scientist, not a philosopher or theologian.

3. Galileo

Galileo’s version of the distinction is more incisive than Êåðler’s and marks an advance in the direction of Descartes. Indeed, it is so close to Descartes that we post-Cartesians are almost bound to read Descartes into it. A careful perusal, however, should suffice to persuade us that there is still a wide gap between Galileo and Descartes. To this end I shall reproduce here in part Burtťs excellent translation of the pertinent passage in Galüeo’s Il Saggiatore, which first appeared in 1623.*

But first I want to propose some examination of that which we call heat, whose generally accepted notion comes very far from the truth if my serious doubts be correct, inasmuch as it is supposed to be a true accident, affection, and quality really residing in the thing which we perceive (sentire) to be heated. Nevertheless I say, that indeed I feel myself impelled by the necessity, as soon as I conceive a piece of matter or corporeal substance, of conceiving that in its own nature it is bounded and figured in such and such a figure, that in relation to the others it is large or small, that it is in this or that place, in this or that time, that it is in motion or remains at rest, that it touches or does not touch another body, that it is single, few or many; in short by no imagination can a body be separated from such conditions: but that it must be white or red, bitter or sweet, sounding or mute, of a pleasant or unpleasant odor, I do not perceive my mind forced to acknowledge it necessarily accompanied by such conditions; so if the senses were not the escorts, perhaps the reason or the imagination by itself would never have arrived at them. Hence I think that these tastes, odors, colors, etc., on the side of the object in which they seem to us to exist, are nothing else than mere names, but hold their residence solely in the sensitive body; so that if the animal were removed, every such quality would be abolished and annihilated. Nevertheless, as soon as we have imposed names on them, particular and different from those of the other primary (primi) and real accidents, we induce ourselves to believe that they also exist just as truly and really as the latter. I think that by an illustration I can explain my meaning more clearly. I pass a hand, first over a marble statue, then over a living man. Concerning all the effects which come from the hand, as regards the hand itself, they are the same whether on the one or on the other object—that is, these primary (primi) accidents, namely motion and contact (for we call them by no other names)—but the animate body which suffers that operation perceives various affections according to the different parts touched, and if the sole of the foot, the kneecap, or the armpit be touched, it perceives besides the common contact, another affection, to which we have given a particular name, calling it tickling. Now this affection is all ours, and does not belong to the hand at all. And it seems to me that they would greatly err who should say that the hand, besides motion and contact, possessed in itself another faculty different from those, namely the tickling faculty; so that tickling would be an accident that exists in it.

This is Galileo at his best: a superb balance of evidence and inference in support of an important conclusion. The conclusion is that since mathematics grasps only the primary qualities of things and since only the primary qualities of things are essential, therefore, our mathematical knowledge of things is essential, i.e., genuine knowledge of nature. This may be “old hat” to us, but it was not to Galileo and his contemporaries. They were accustomed to expressing natural knowledge in the Aristotelian terms of substance, accident, form, genus and difference, act and potency. Now of a sudden this is all to be swept aside and replaced by a new vocabulary of motion expressed in the symbols of mathematics. The impact of this innovation must have been enormous.

Our interest here, however, is not in this conclusion or its novelty, but in the argument itself and the view it takes of the secondary qualities. They are not essential, i.e., they do not attach to things as they are in themselves, but are only ascribed to things by a sentient body which perceives them. When a sentient body perceives anything by its senses, secondary qualities are produced or caused in its sense organs by external causes which are moving bodies possessing only primary qualities. In this sense the secondary qualities exist only “in us,” i.e., in our “animate and sensitive bodies,” not in the things perceived. Hence if all animate and sensitive bodies were removed, and therewith all sense perception, all secondary qualities of things would also be removed and bodies would then be seen to possess only their essential primary qualities.

Notice that Galileo has not banished secondary qualities from the world. They exist for him in our objective sense organs, where they occur as objective effects of objective causes. Just because they are objective effects they can be used as “indices” of their causes. But as effects they cannot be ascribed to their causes as properties; and they obviously do not reside in all bodies since they are restricted in their occurrence to sensitive bodies only. Subjective is hardly the adjective to apply to them; for they are not mental entities, as opposed to physical, and hence not properly sensations or impressions or “ideas”; this is all to come later. “Relative” is the better adjective; for they are relative to our sense organs, fleeting in their occurrence, and inadequate, as effects, to characterize their causes. This is all that Galileo is saying about secondary qualities. This is enough, since it adequately prepares the way for applying mathematics to the primary causes which underlie the secondary qualities.

Thus Galileo, no more than Kepler, was advancing a new theory of sensation. The very notion of sensation, so familiar to us, was quite foreign to both Kepler and Galileo, indeed to all who preceded Descartes. The Latin words sensatio and impressio did not mean for them what the English words “sensation” and “impression” have come to mean for us, namely, a purely “subjective” sense datum residing wholly in the mind or consciousness. To be sure, the sensible qualities of things are for Galileo relative, fleeting effects. We would say at once that they are “subjective” with all that this implies. But this is not what Galileo said or meant. He did not “subjectivize” the secondary qualities. With the restraint of the disciplined inquirer he was attempting to draw an empirically grounded distinction between the primary and secondary qualities of things for the sovereign purpose of facilitating the application of mathematics to natural phenomena.

If Galileo did not go on to resolve the philosophic problems which his distinction raised, it was not because he was unaware of these problems or of the explosive threat which they posed to the scholastic notions then prevailing. It was because of his consuming interest in natural science. Now it is the good fortune of natural science that it does not have to wrestle with such problems philosophical; once its own needs are met it can blithely ignore them and resume its triumphant course. Galileo saw this clearly and with eminent good sense left these problems as he found them: as issues to confound the philosophers, not as roadblocks to impede natural inquiry.

What are the philosophic problems which the distinction between primary and secondary qualities raises? Perhaps the most obvious problem is this. If all bodies have only primary qualities, must not sentient bodies, as bodies, have only primary qualities? If so, how then can sentient bodies, any more than insentient bodies, offer sanctuary to secondary qualities? Another way of putting this is: how can any body possessing only primary qualities possess also the “quality” or “faculty” of sentience? For whatever sentience may be it is not a primary quality. Nor is it a secondary quality, although it involves secondary qualities. But how? Clearly the problem is not confined to bodies as bodies and their inherent qualities; it pertains also to the whole nature of sentience, of sense perception. If Galileo was aware of this problem he made no effort to solve it.

He did solve, however, another problem which is closely connected with the first. This problem we have already raised. What precisely is the difference between the two kinds of qualities? In declaring the secondary qualities to be but fleeting effects produced in our sense organs by more permanent primary causes, Galileo was saying that the two differ in the first instance as cause and effect and that the primary qualities enjoy the priority which usually attaches to the cause. But is it empirically evident that they differ as cause and effect?

If the question is one of empirical evidence, then I must urge once again the importance of the three observations which I made in the preceding chapter. 1) Primary and secondary qualities are so fused together as to be actually inseparable, so that although distinguishable in idea they are inseparable in fact. 2) They are both perceived “out there” in precisely the same sense as “objective” qualities of things, not as “residents” of our sense organs (and certainly not as “subjective” contents of our minds). 3) They are both perceived through the same organs of sense; it is only when these organs are stimulated that we perceive anything at all, and then always both primary and secondary qualities together; to this extent the primary qualities are just as “sensible” and sense-dependent as the secondary.

In the light of these three empirical observations it is definitely not empirically evident that primary and secondary qualities differ as cause and effect. But how then do they differ—granting that they actually do? It is not my intention here to answer this question, but to raise it, to insist on its importance in any philosophy of science, and to warn us that its answer is to be got not by hypothetical arguments, but by a careful analysis of such empirical data as are set forth in the three observations above. Only by analyzing and conciliating these inviolable matters of evidence can the distinction be clarified and rendered philosophically acceptable.

Galileo and Descartes were quite unaware of this need for clarification and hence were not inclined to any such program of analysis and conciliation. The evidence they adduced was sufficient to persuade them that primary and secondary qualities differ as cause and effect. In their eagerness they failed to note that other evidence, equally pertinent, casts serious doubt on this difference. And so without further ado they adopted the distinction as drawn, and used it each for his own purposes. Galileo used it as a device to further the application of mathematics to nature. Descartes saw in it a new theory of sensation (or “ideas”) and through this theory a pair of corollaries which called for a complete revision of human know!edge, a revision to be carried out by that selfsame reason which was disporting itself so brilliantly in the new mathematics and science. As Galileo was promoting a new method of natural inquiry, Descartes was inaugurating a new tradition of philosophy and prescribing for this tradition the basic terms in which the central problem and its solution were to be couched, those namely of the theory of sensation.

Had not Galileo distinguished primary from secondary qualities, as cause from effect, I strongly suspect that neither Descartes nor anyone else would have thought of sensations. But as it was, the distinction being given, Descartes extracted from it his momentous theory of sensation, not by analysis and conciliation, but by argument and inference, in accordance with his own principles of “method.” Let us now turn to Descartes’s classic argument for sensations.

*Quoted in Edwin A. Burtt, Metaphysical Foundations of Physics, p. 57. In this account of Kepler and Galileo I also lean heavily on Ernst Cassirer, Erkenntnis Problem, Vol. 1.

*Burtt, pp. 75f. My friend and colleague Professor Floyd Zulli assures me that this translation is quite adequate.