What is Life? Were such a question proposed, we should be tempted to answer, what is not Life that really is? Our reason convinces us that the quantities of things, taken abstractedly as quantity, exist only in the relations they bear to the percipient; in plainer words, they exist
common character of a whole class in the nomenclature of botany would enable a person to understand all, or any one of the plants contained in that class. But if, on the other hand, the machine in question were such as no man was a stranger to, if even the supposed peculiarity, either by its effects, or by the construction of that portion of the works which produced them, were equally well known to all men, in this case we can conceive no use at all of such a definition; for at the best it could only be admitted as a definition for the purposes of nomenclature, which never adds to knowledge, although it may often facilitate its communication. But in this instance it would be nomenclature misplaced, and without an object. Such appears to me to be the case with all those definitions which place the essence of Life in nutrition, contractility, &c. As the second instance, I will take the inventor and maker of the machine himself, who knows its moving power, or perhaps himself constitutes it, who is, as it were, the soul of the work, and in whose mind all its parts, with all their bearings and relations, had pre-existed long before the machine itself had been put together. In him therefore there would reside, what it would be presumption to attempt to acquire, or to pretend to communicate, the most perfect insight not only of the machine itself, and of all its various operations, but of its ultimate principle and its essential causes. The mysterious ground, the efficient causes of vitality, and whether different lives differ absolutely or only in degree, He alone can know who not only said, "Let the earth bring forth the living creature, the beast of the earth after his kind, and it was so;" but who said, "Let us make man in our image, who himself breathed into his nostrils the breath of Life, and man became a living soul.
The third case which I would apply to my own attempt would be that of the inquirer, who, presuming to know nothing of the power that moves the whole machine, takes those parts of it which are presented to his view, seeks to reduce its various movements to as few and simple laws of motion as possible, and out of their separate and conjoint action proceeds to explain and appropriate the structure and relative positions of the works. In obedience to the canon,—"Principia non esse multiplicanda præter summam necessitatem cui suffragamur non ideo quia causalem in mundo unitatem vel ratione vel experientiâ perspiciamus, sed illam ipsam indagamus impulsu intellectûs, qui tantundem sibi in explicatione phænomenorum profecisse videtur quantum ab codem principio ad plurima rationata descendere ipsi concessum est."
