ABSTRACT
This chapter attempts to determine the adequacy of pictorial knowledge. Regardless of the stage which this type of knowledge may occupy in the development of knowledge as a whole, it is clearly a kind of knowledge making a certain claim to adequacy. As a consequence actual material models, constructed out of string, rubber, pulleys, and wire, become a special case within the general treatment. The construction of materal models for thought images is simply an attempt to overcome the fluctuating character of the symbol and does not change the problem in its essential details. Word symbols are more adequate than icons in the representation of fields where our knowledge is internally contradictory. One might well insist that the difficulties which are inherent in Lord Kelvin’s portrayal of the ether are not features of the symbolism but the expression of a fundamental irrationality in the ether itself.
