In like manner Professor Huxley,[28] undertaking to vindicate full scientific value for his own favourite Biology, does so by pointing out that biological methods are similar to those of every other branch of Science, since they begin with the observation of facts, and from this proceed to various applications of the knowledge so acquired. And Professor Haeckel himself tells us regarding his own mode of procedure:[29] The means and methods we have chosen for attaining the solution of the great enigma do not differ, on the whole, from those of all purely scientific investigation: firstly, experience; secondly, inference. Therefore, although the phrases we have already heard from him, are found when scrutinized to be only phrases, which explain nothing, it may be supposed that he elsewhere produces such proofs of his doctrine as will place it on a scientific basis. For these we will now seek. VI "THE LAW OF SUBSTANCE" We have just been told by Professor Haeckel, that the means and methods which he has chosen for the establishment of his philosophy are, on the whole, identical with those employed in all purely scientific investigation, namely, first experience, and secondly inference. But here a grave difficulty at once presents itself. How, either by experience or by inference, can we learn anything about the commencements of the universe, as to which we have heard so much? How the first bodies, whether organic or inorganic, actually arose, neither philosophy nor science can definitely say, for the latter was not there to see, and the former has no facts on which to argue.[30] But if neither by observation, nor by clear inference, can the account that has been given be substantiated, that account cannot pretend to be scientific, for it rests not upon knowledge but upon speculation,--and as Professor Tait warns us,[31] "That of which there is no knowledge is not yet part of Science."