The human being, on the other hand, is firmly located in a temporal process. He has an image of the past which extends back far beyond the limits of his own life and experience, and he likewise has an image of the future. Closely associated with the time structure of his image is the image of the structure of relationships. Because we are aware of time, we are also aware of cause and effect, of contiguity and succession, of cycles and repetition. The image of man is also characterized by a much greater degree of self-consciousness and of self-awareness than that of the lower animals. We not only know, but we know that we know. This reflective character of the human image is unique, and is what leads to philosophy.

p. 25 - The Image: Knowledge in Life and Society, 1956