We are dealing with facts of Life, with collective mental function in action, and we can appeal, therefore, to the principles of general biology to guide us. We can, for example, since every organism bears in its structure not only the record of its own life-history but the vestiges of its ancestry, confidently expect to find in the traits of nations the survivals of their earlier and unrecorded conditions.
Understood in this sense, ethnic psychology does not deal with mathematics and physics, but with collections of facts, feelings, thoughts, and historic events, and seeks by comparison and analysis to discover their causal relations. It is wholly objective, and for that reason eminently a “natural” science. The objective truths with which it deals are not primary but secondary mental products, as they are not attached to the individual but to the group. For this reason it has an advantage over other natural sciences in that it can with propriety search not only into growth but into origins, for, in its purview, these fall within the domain of known facts.
We must recognise that the psychical expressions of life are absolutely and always correlated to the physical functions and structure; and that, therefore, no purely psychical causes can explain ethnic development or degeneration. As the past of an organism decides its future, so the future of a people is already written in its past history.
As in ethnic psychology the material is different from that in experimental psychology, so in the former we must abandon the methods suitable in the latter. The ethnic _psyche_ is made up of a number of experiences common to the mass, but not occurring in any one of its individual members. These experiences of the aggregate develop their own variations and modes of progress, and must be studied for themselves, without reference to the individual, holding the processes of the single mind as analogies only.
While fully acknowledging the inseparable correlation between all psychical activities and the physical structures which condition them, let us not fall into the common and gross error of supposing that physical is in any way a measure of psychical function. All measurements in experimental psychology, be they by chemistry or physics, are quantitative only, and can be nothing else (Wundt); whereas psychical comparisons are purely qualitative.