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and the law has thus been so far simplified, that it is now comprehended under the more general laws of the perpetuation of living beings on the earth's surface. The cause of life is just as distant and as obscure as before.
One more lesson let me deduce from the discordant views of these philosophers. In limine the questioning of Nature should have proceeded from both in the very same form; the answers could not otherwise be in harmony. It is very remarkable that later observations have shown that there were special circumstances affecting Bastian's solution, not present in Tyndall's, which made it of some importance that the formula should have been exactly copied. On the other hand, it seems almost incredible that a law of Nature should have been based on a single instance, when all other experiments on similar substances failed to confirm it. In fact, it ought to have been regarded simply as an exception to the law, and the modifying circumstances closely investigated.
In attempting, then, to give a definition of the term "law," I wish merely to place before you the idea of what is present to my own mind in its employment. It may be regarded as a short statement of the certainty arrived at by our reason, that out of one condition another necessarily arises, and that the two conditions are associated together by some principle or mode of causation which may or may
