210 H. SIDGWICK : condition and relations of the things that we are examining with the question by what process they have come to be what they are : the actual resemblances and differences between (e.g.) an ape and an ascidian remain obviously just the same whether we affirm or deny that the former has been developed out of the latter. But in the investigation of mind owing to the greater difficulty and obscurity of sub- jective observation and analysis a confusion of this kind has been possible and has actually taken place. When it has been shown with more or less probability how thought may have gradually grown from sensation, rational choice from instinctive impulse, altruism from egoism, it has been hastily inferred that the nature of thought, will, disin- terested desire is somehow altered by the discovery of their historical antecedents : that these later and higher mental facts are not what they seem, what subjective introspection and analysis declare them to be, but something different namely, the more primitive phenomena which have preceded them in development : that thought is a species of sensa- tion, altruism a species of egoism, and so forth. It always seems to me that this inference, though it has been widely made, admits of no justification when the question of its legitimacy is once distinctly raised. As I have elsewhere said (Methods of Ethics, 209), it seems to have been encouraged "by an infelicitous transference of the conceptions of chemistry to psychology : the later mental phenomenon is supposed to be a quasi-chemical compound of the antece- dent phenomena from which it has been derived. But in chemistry this conception is legitimated by the ascertainable equality in weight between compound and elements and the possibility of substituting the latter for the former : but no such reasons exist nor any others that I know of for con- sidering psychical antecedents as really constitutive of their psychical consequents in spite of their apparent dissimi- larity." But, it may be said, granting that the question what our thoughts, emotions or volitions actually are cannot be affected by any investigation of the process by which they have come to be what they are, still such investigation may have an important bearing on the more interesting because more difficult question, whether they are what they ought to be. The method of introspective observation, it may be said, has commonly professed to do more th;in give us a mere inventory of our thoughts ; it has professed to give us a criterion for determining their validity ; and it is this pre- tension rather than the former that has been successfully
