subjectively necessary (as a law of nature) is objectively a very contingent practical principle, which can and must be very different in different subjects and therefore can never furnish a law; since, in the desire for happiness it is not the form (of conformity to law) that is decisive, but simply the matter, namely, whether I am to expect pleasure in following the law, and how much. Principles of self-love may, indeed, contain universal precepts of skill (how to find means to accomplish one's purpose), but in that case they are merely theoretical principles; * as, for example, how he who would like to eat bread should contrive a mill; but practical precepts founded on them can never be universal, for the determining principle of the desire is based on the feeling pleasure and pain, which can never be supposed to be universally directed to the same objects. * Propositions which in mathematics or physics are called practical ought properly to be called technical. For they have nothing to do with the determination of the will; they only point out how a certain effect is to be produced and are, therefore, just as theoretical as any propositions which express the connection of a cause with an effect. Now whoever chooses the effect must also choose the cause. {BOOK_1|CHAPTER_1 ^paragraph 40} Even supposing, however, that all finite rational beings were thoroughly agreed as to what were the objects of their feelings of pleasure and pain, and also as to the means which they must employ to attain the one and avoid the other; still, they could by no means set up the principle of self-love as a practical law, for this unanimity itself would be only contingent. The principle of determination would still be only subjectively valid and merely empirical, and would not possess the necessity which is conceived in every law, namely, an objective necessity arising from a priori grounds; unless, indeed, we hold this necessity to be not at all practical, but merely physical, viz., that our action is as inevitably determined by our inclination, as yawning when we see others yawn. It would be better to maintain that there are no practical laws at all, but only counsels for the service of our desires, than to raise merely subjective principles to the rank of practical laws, which have objective necessity, and not merely subjective, and which must be known by reason a priori, not by experience (however empirically universal this may be). Even the rules of corresponding phenomena are only called laws of nature (e.g., the mechanical laws), when we either know them really a priori, or (as in the case of chemical laws) suppose that they would be known a priori from objective grounds if our insight reached further. But in the case of merely subjective practical principles, it is expressly made a condition that they rest, not on objective, but on subjective conditions of choice, and hence