I was rereading portions of Russell’s Human Knowledge (and making comparisons to The Analysis of Matter) with the goal of understanding his arguments regarding the role of structure in linking experience to the physical world. But I was struck by something else. At the end of the book, his conclusions regarding how scientific inferences are justified trace this question back to the prior question of how we gain knowledge of causation. Causation is presumed in science, but causation is itself not explicated or justified within science: it is a pre-scientific concept.
A main project in Human Knowledge is to identify those unacknowledged postulates which undergird our scientific pursuit of knowledge: “what must we be supposed to know, in addition to particular observed facts, if scientific inferences are to be valid?” (p.513). He ends up with five postulates in total, but notably it turns out all of them “involve the concept of ‘cause’” (p.508).
How do we know these postulates, then, if indeed we do know them, given their reliance on our knowledge of causation? Russell can only point to our gaining a primitive grasp on cause via our pre-linguistic biological know-how: “Knowledge of general connections between facts has its biological origins in animal expectations “(p.514). It was advantageous in evolutionary terms for our animal expectations to roughly conform to processes in the physical world. The physical world apparently has causal laws, and animal inferences are adapted to these.
When evaluating the thesis of empiricism, Russell understands that strictly speaking this kind of knowledge is something beyond experience (at least as these terms are usually employed in the debate): “Either, therefore, we know something independently of experience, or science is moonshine” (p.524).