…according to the law of dynamics, no change of motion can take place except through accelerations which are dependent exclusively upon the mutual positions of particles or parts of matter; and according to the law of mind, no idea can arise except by virtue of an association. These propositions cannot properly be said to be proved; but they are postulated; and for the sake of argument we may admit that they are strictly true.
http://www.commens.org/dictionary/entry/quote-minute-logic-chapter-ii-prelogical-notions-section-i-classification-scienc-35