TWO SORTS OF KNOWLEDGE?

A lot of our knowledge derives from sense experience: from what we see, hear, touch, etc. Other things we know – about mathematics and logic, for example – seem quite independent of sense experience; we know them simply by thinking – about, for example, the definition of a triangle or the meaning of the term “implies.” Philosophers have long recognized this fact by a distinction between knowledge that is a posteriori (derived from sense experience) and knowledge that is a priori (derived from mere thinking, independent of sense experience). This distinction concerns the ways in which we know. Two further distinctions suggest themselves, one concerning what our knowledge is about (its content) and the other concerning its stability (or, to use the standard logical term, its modality). First, there is a distinction between knowledge about the world we encounter through our experience and knowledge derived from the meanings of the concepts (or words) we use to think. Philosophers, at least since Kant, have called knowledge about the world synthetic, and knowledge about meanings analytic. Second, there is a distinction between knowledge that is contingent (about what can change, such as the color of a leaf) and knowledge that is necessary (about what cannot change, such as the fact that blue is a color).

Philosophers have focused intensely on these distinctions, not only because they seem important for understanding knowledge in general but also because they seem crucial for understanding the nature of philosophical knowledge itself.