ABSTRACT
In the last book that Whitehead wrote there is a passage which every April brings to my mind. He is insisting that all human understanding is partial, but without permanent limits. "For example, we know about the colour 'green' in some of its perspectives. But what green is capable of in other epochs of the universe, when other laws of nature are reigning, is beyond our present imaginations. And yet there is nothing intrinsically impossible in the notion that, as years pass, mankind may gain imaginative insight into some alternative possibility of nature, and may therefore gain understanding of the possibilities of green in other imagined epochs."I
In what other philosopher's writings could we expect to find what the professionals call a 'sense-datum term' being used at once to call attention to the immediate value of sensory experience, to remind us of our ignorance, and to set forth the ideal of ever enlarging our conceptual horizons? My purpose in quoting the passage, however, is not to contrast various uses of sense-datum terms. It is to indicate one of the kinds of caution which a good metaphysician should have. What he hopes is a quite general theory of existence may, for all he knows, be quite as special as three-dimensional Euclidean geometry. This caution is consequent upon a bold imagination concerning possibilities. The boldness makes trouble; there are obvious difficulties in the idea of a presumably infinite variety of cosmic epochs, and (for me) in the idea of an eternal object, like green. I shall look at the second later. My present point is only that a metaphysics which does not boldly make a generous allowance for forms of existence "beyond our present imaginations", is in danger of a dogmatic provincialism.
