The conflicts which I had so often had to sustain in defending the theory of government laid down in Bentham’s and my father’s writings, and the acquaintance I had obtained with other schools of political thinking, made me aware of many things which that doctrine, professing to be a theory of government in general, ought to have made room for, and did not. But these things, as yet, remained with me rather as corrections to be made in applying the theory to practice, than as defects in the theory. I felt that politics could not be a science of specific experience; and that the accusations against the Benthamic theory of being a theory, of proceeding à priori by way of general reasoning, instead of Baconian experiment, showed complete ignorance of Bacon’s principles, and of the necessary conditions of experimental investigation. At this juncture appeared in the Edinburgh Review, Macaulay’s famous attack on my father’s Essay on Government. This gave me much to think about. I saw that Macaulay’s conception of the logic of politics was erroneous; that he stood up for the empirical mode of treating political phenomena, against the philosophical; that even in physical science his notion of philosophizing might have recognized Kepler, but would have excluded Newton and Laplace. But I could not help feeling, that though the tone was unbecoming (an error for which the writer, at a later period, made the most ample and honourable amends), there was truth in several of his strictures on my father’s treatment of the subject; that my father’s premises were really too narrow, and included but a small number of the general truths, on which, in politics, the important consequences depend. Identity of interest between the governing body and the community at large, is not, in any practical sense which can be attached to it, the only thing on which good government depends; neither can this identity of interest be secured by the mere conditions of election. I was not at all satisfied with the mode in which my father met the criticisms of Macaulay. He did not, as I thought he ought to have done, justify himself by saying, “I was not writing a scientific treatise on politics, I was writing an argument for parliamentary reform.” He treated Macaulay’s argument as simply irrational; an attack upon the reasoning faculty; an example of the saying of Hobbes, that when reason is against a man, a man will be against reason. This made me think that there was really something more fundamentally erroneous in my father’s conception of philosophical method, as applicable to politics, than I had hitherto supposed there was. But I did not at first see clearly what the error might be. At last it flashed upon me all at once in the course of other studies. In the early part of 1830 I had begun to put on paper the ideas on Logic (chiefly on the distinctions among Terms, and the import of Propositions) which had been suggested and in part worked out in the morning conversations already spoken of. Having secured these thoughts from being lost, I pushed on into the other parts of the subject, to try whether I could do anything further towards clearing up the theory of Logic generally. I grappled at once with the problem of Induction, postponing that of Reasoning, on the ground that it is necessary to obtain premises before we can reason from them. Now, Induction is mainly a process for finding the causes of effects: and in attempting to fathom the mode of tracing causes and effects in physical science, I soon saw that in the more perfect of the sciences, we ascend, by generalization from particulars, to the tendencies of causes considered singly, and then reason downward from those separate tendencies, to the effect of the same causes when combined. I then asked myself, what is the ultimate analysis of this deductive process; the common theory of the syllogism evidently throwing no light upon it. My practice (learnt from Hobbes and my father) being to study abstract principles by means of the best concrete instances I could find, the Composition of Forces, in dynamics, occurred to me as the most complete example of the logical process I was investigating. On examining, accordingly, what the mind does when it applies the principle of the Composition of Forces, I found that it performs a simple act of addition. It adds the separate effect of the one force to the separate effect of the other, and puts down the sum of these separate effects as the joint effect. But is this a legitimate process? In dynamics, and in all the mathematical branches of physics, it is; but in some other cases, as in chemistry, it is not; and I then recollected that something not unlike this was pointed out as one of the distinctions between chemical and mechanical phenomena, in the introduction to that favourite of my boyhood, Thomson’s System of Chemistry. This distinction at once made my mind clear as to what was perplexing me in respect to the philosophy of politics. I now saw, that a science is either deductive or experimental, according as, in the province it deals with, the effects of causes when conjoined, are or are not the sums of the effects which the same causes produce when separate. It followed that politics must be a deductive science. It thus appeared, that both Macaulay and my father were wrong; the one in assimilating the method of philosophizing in politics to the purely experimental method of chemistry; while the other, though right in adopting a deductive method, had made a wrong selection of one, having taken as the type of deduction, not the appropriate process, that of the deductive branches of natural philosophy, but the inappropriate one of pure geometry, which, not being a science of causation at all, does not require or admit of any summing-up of effects. A foundation was thus laid in my thoughts for the principal chapters of what I afterwards published on the Logic of the Moral Sciences; and my new position in respect to my old political creed, now became perfectly definite.
Note from KBJ: This paragraph illustrates how Mill solved problems. Notice the element of serendipity. While working on one topic (natural philosophy), Mill gained insight into another (political philosophy).
