I now proceed to the second point of criticism, which strikes at the heart of Kant’s ethics. Man according to Kant is worth while on his own account (an end per se), never to be used as a mere tool or thing. He is a person, an object towards whom we are bound to evince absolute respect. Yet Kant immediately goes on to say that there is no object in all the world, neither man nor any other, that is worth while on its own account, that deserves such respect. Kant’s views of actual human nature are tinged with somber pessimism. (Compare the chapter on Radical Evil in his Religion Within the Limits of Pure Reason.) A strange paradox is thus presented to us. Man is to be accepted as a worth while object, and yet there is no worth while object. How does Kant seek to escape from this predicament? He says, not the man primarily, but something that happens in the man, is supremely significant: certain acts are worth while on their own account,—the agent only in so far as he performs such acts (or, let us add with a sigh, as he tries to perform them)—namely, acts which have as their sole motive respect for universal law. Then he informs us that similar processes occur in other agents, in fellow human beings, or, more precisely, that these others are capable of trying to act83 as I myself feel bound to try to act. Consider how far fetched is the argument, on what wavering foundations has been placed the ethical pronouncement of human worth and human equality in which our interest is so profoundly engaged. We do wish to be assured of this cardinal truth. No other truth is practically and theoretically of greater importance. As against the iniquitous practices of the world, as against the exploitation of labor, as against the degradation of woman, as against political tyranny whether exercised by kings or by mobs, we raise up for our shield the indefeasible worth of men—not of some men but of all men. And now, behold! the thinker to whom we owe the forcible expression of this truth seems to have left it in the air. I scrutinize my neighbors, and find in their behavior no sure sign of real worth. I fall back on myself and I discover what? The idea of an act which, if I could perform it, would stand on its own merits (would be self-justified). I then find that I am bound to try to perform such acts. I cannot affirm that in a single instance I have ever performed such an act. I next infer—on what tenuous ground has been shown in the last chapter—that my fellow-beings have the same inner experience as mine. And it is for this reason that by a circuitous inference I declare them to be worth while objects.  
That Kant has formulated a truth of the utmost importance for mankind (that no man is to be treated as a mere tool), seems to me incontestable. That he has not made good his own proposition is my contention, and that the whole problem must therefore be taken up de novo. It will assist us in doing so to expose the84 flaw in his categorical imperative, or the formal principle of universality and necessity applied to human actions, which in his view imprints upon them the character of absolute rightness.
 
Note that Kant approaches the problems of ethics from the side of physical science, and with the bias of the physical scientist. The ethical principle he sets up, the bare idea of universal necessity or of law in general, is derived by way of abstraction from the particular laws of nature. It is a physical principle in disguise. To understand Kant’s system, it is simply indispensable to keep this point in mind. He was pre-occupied during the major portion of his life with profound speculations on scientific subjects. The title of the Critique of Pure Reason might not be inappropriately changed into “A treatise on the fundamental assumptions of science, as handled by Newton and his successors.” He was undeniably interested in ethics. His ultimate aim was to clear the way for the confident holding of ethical principles. (See the Preface to the Critique of Pure Reason.) But he could not divest himself of the prejudice of his temperament and of his lifelong pursuit. He is not singular in this respect. To borrow the first principle of ethics from some other field is a common and apparently ineradicable error. Mechanics, ?sthetics, and recently biology, have been laid under contribution for this purpose. A consistent attempt to study ethical phenomena on their own ground, to mark off what is really distinctive in the data of ethical experience, and then to search for some principle which shall serve to give a coherent account of them, has to my85 knowledge never yet been undertaken. Always ethics has been treated as an annex to some other discipline. Always we behold the attempt to assimilate before the distinctive traits and characteristics have been carefully investigated. Never yet has the independence of this wonderful aspect of human nature been truly acknowledged. Kant indeed freed ethics from its long tutelage to theology; but he left it still in subjection, subject to his own favorite study, physical science.
 
But though the notion of necessity, together with that of universality, which he derived from physics was employed by him as a fundamental principle of rightness in conduct, the principle itself insensibly, and as it would seem unbeknown to himself, underwent a remarkable change in the course of his undertaking to give it a new application. The following brief comments will serve to elucidate this point.
 
In physics, whenever an antecedent phenomenon has been exactly described, and a sequent phenomenon is defined in the same fashion, the connection is pronounced to be necessary—as for instance the transformation of mechanical energy into heat, and conversely. A single carefully guarded experiment may suffice to establish the necessary nexus between two phenomena. And after having established the necessity, we are confident of the universality. If exceptions should occur and contravene the supposed law, the calculations or the observations are to be corrected. But never in physical science do we start from universality and predict necessity therefrom. Kant in his ethics invariably couples to............