From the observation of several parallel instances, philosophers form a maxim that the connexion between all causes and effects is equally necessary, and that its seeming uncertainty in some instances proceeds from the secret opposition of contrary causes. Thus, for instance, in the human body, when the usual symptoms of health or sickness disappoint our expectation; when medicines operate not with their wonted powers;
Zenbait kasu paraleloren behaketatik, filosofoek printzipioa ezartzen dute ezen kausa guztien eta efektu guztien arteko konexioa berdin dela beharrezko, eta beronen itxurazko ziurtasun eza, kasu batzuetan, kontrako kausen oposizio ezkututik datorrela.