(The memorable example for me: If I observe that the sidewalk is wet, I take regard this as evidence that it rained last night. If I wash the sidewalk with a hose, and then observe it to be wet…. I find that many formalisms cannot represent the situation. Ooops.)

The two are closely linked conceptually, and William W. Bartley III, who studied under Popper, was a founder of what is called “evolutionary epistemology”. I think that evolutionary epistemology is the right approach to the fundamental question of how knowledge emerged in a world that began as accreted rock and progressed to worms with eyes long before the first ape, or the first spoken word.

Dogs acquire knowledge through life experience, and plant species acquire knowledge — in the sense of an alignment of implicit expectations and behaviors with reality — through what might be called “evolutionary experience”. Any philosophy that cannot see these as kinds of knowledge seems to me to be radically defective, and prone to losing itself in word games, or to plunging into another fruitless search for a deep, solid, indisputable “foundation of knowledge”.

Human knowledge is a great web of densely connected parts, not a stack of blocks with a bottom that must rest on something else. It has central and peripheral regions, perhaps, but not a top or bottom.