that individual development or ontogeny repeats in a general way race development or phylogeny. The designation and systematization and organization of sense impressions, on the one hand, and subjective states on the other, which are the very essence of rational life, and which distinguish the civilized man from the savage, and the adult from the child, are found on closer examination to consist fundamentally, as to fully one half at least, in naming and placing and correlating the attributes of natural objects.
Turning now from the racial and the individual development of ordinary rational life, to the development of physical science, we may characterize this development by saying that its whole course has been one of discovery of new natural bodies each having its own attributes; and of new attributes of old bodies, that is, of bodies already known.
The attributes of bodies, with many for each body, are the very cement and sand and gravel and steel out of which the reinforced concrete edifices of experiential knowledge, both common and scientific, are built up; and any one who comes forward with a hypothesis of nature which in essence declares that some single one of these building materials is all that nature really furnishes so that the edifice of knowledge must get along with only this one, is presenting a daring hypothesis sure enough. If true it must, of course, be accepted; but no one should fail to see that its complete acceptance would mean the complete demolition of the great edifices of common knowledge and physical science as these have been laboriously built up through the centuries, and the erection on their sites of other edifices wholly different in design and construction. Surely the proof in support of so revolutionary a hypothesis must be convincing beyond a shadow of doubt. Is it? For one I am convinced it is not. Were there no other grounds for doubting the electrical theory of matter and so of all nature, a sufficient one is found in the circumstance already alluded to, namely that no physical observation or experiment ever gets rid of the "probable error"; and that in this probable error there is always a chance of an unknown factor in the phenomena under investigation.
So I turn again to the natural history way of viewing the world and point out that it is in strict accord with both the historic development of natural knowledge and the fundamental processes of psychic life in that it accepts without cavil the whole range of attributes of natural bodies, demanding only that these be undoubted as to identification. It is only when the natural history attitude and the materialistic attitude toward nature is each viewed in its mode of treating the attributes of natural objects, that the fundamental distinction between the two attitudes comes to view. The natural history attitude is one of unreserved acceptance of the world of fact, one of its greatest concerns being to make sure of what the facts are. It makes no such sharp distinction between fact
