82 INTRODUCTION TO PHILOSOPHY OF SCIENCE 



in its formulation. In fact one may say that when the com- 

 mon sense theory becomes formulated it has already become 

 critical and has ceased to be the position of the ordinary 

 man. The purpose in examining it here is to draw con- 

 clusions as to the possibility of making it a foundation 

 for scientific procedure. Science is often described as 

 continuous with common sense and as differing from it 

 only in the degree of criticism which is introduced. This 

 suggests that some light may possibly be thrown on science 

 by examining common sense. 



The theory is usually described as representative in char- 

 acter. It maintains that what is known through perception 

 is a realm of material objects existing in space and time, 

 and possessing certain properties such as shape, size, rest 

 or motion, color, sound, hardness, and on certain occasions, 

 taste, and odor. Sense perception is a process of receiving 

 from the material objects physical stimuli which enter the 

 sense organs and are transmitted through the nervous sys- 

 tem to the brain and thence into the mind. Knowledge is a 

 complex of immaterial entities called ideas, located some- 

 how in the mind, which is itself vaguely associated with 

 the brain and therefore presumed to be in the skull. The 

 ideas are consequently not in space or time in any precise 

 sense and they do not exhibit any of the properties of 

 physical objects such as hardness, rest, motion, shape, or 

 color. But they have the peculiar power of mirroring the 

 properties of physical objects, and are thus instruments of 

 knowledge. When they correspond to objects they are true 

 and constitute knowledge; when they fail to correspond 

 they are false and constitute error. The knower functions as 

 the recipient of the stimuli and as the residence of the ideas. 



It requires no careful analysis to justify the conclusion 

 that such a theory of cognition can hardly be adequate as 

 an interpretation of science. Philosophy has long been 

 wrestling with this problem and has brought certain of the 

 difficulties inherent in it clearly to light. Two of its inade- 

 quacies may be suggested here. In the first place, no satis- 



