Note 167 — Chapter VI · THE LOGICAL CHARACTER OF DESCRIPTIVE SCIENCE
Reading edition
If we merely desired to fix the sense of the term mass without introducing the concept of constant mass, we might of course consider two bodies only, A and B. Then the ratio mass of B ——— mass of A = acceleration of A in presence of B ————————————— acceleration of B in presence of A. See Mach, Science of Mechanics, p. 216 ff.; and Pearson, Grammar of Science, p. 302 (2nd ed.), on which the above account is based.