IV. TESTIMONY AND AUTHORITY. BY A. F. EAVENSHEAR. I. THE CLAIMS OF TESTIMONY. IN the best scientific work, even as in the worst, much must be taken upon trust ; on the authority of the competent observer, skilled instrument maker, or original investigator. The Chemist, in establishing the existence of a new com- pound, or defining its properties, relies to a great extent upon the determinations of others as to the atomic weights, formulae, densities, specific heats, boiling-points, refractive indices and other coefficients of the auxiliary substances or reagents he employs. In much of his apparatus weights, balances, polarimeters he relies upon the work of the instrument maker. The Physicist in like manner employs all such results as are in general repute tabulated densities, temperature-coefficients, elasticities, weights, resistances. The Astronomer makes use of the observations of his pre- decessors, as well as of his contemporaries in distant ob- servatories. The acceptance of observations and descriptions in this manner is still more marked in geology, zoology, botany. The disposition of rocks in various countries and the occurrence of minerals ; the kinds and distribution of plants and animals ; all are to any given systematise!" largely matters of report. It might indeed seem that, in physical science, time and opportunity alone are needed to enable a man of sufficient energy and capacity to do the work of a hundred observers. But in psychology it is far otherwise ; for, whatever his capacity, one man knows only one mind. Eeliance upon others in physical science may be merely unavoidable ; but to Psychology it is essential. Inductive Logic, in so far as it claims to be a theory of Scientific Method, ought then to include a theory of Testi- mony and Authority. But in the current treatment this seems to a great degree to be lost sight of. We are presented with a theory of scientific method conceived as followed out by an investigator working alone, and almost from the
