^ WHAT IS SCIENCE? 



ARE THEORIES REAL ? 



And here we come to our last question. I have been 

 at pains to distinguish theories from laws, and to insist 

 that theories are 'not laws. But if that contention is 

 true, are not theories deprived of much of their value ? 

 Laws, it may be said, are statements about real things, 

 about real substances (such as iron), about real objects 

 (such as the earth or the planets or existing living beings). 

 Laws are valuable because they tell us the properties of 

 these real objects. But if theories are not laws, and if the 

 statements they make are about things that cannot ever 

 be the subject of laws, do they tell us about anything 

 real ? Are the molecules (by means of which we explain 

 the properties of gases) or the countless generations of 

 unknown animals and plants (by means of which we 

 explain the connexions between known animals and 

 plants) or the forces on the planets (by means of which 

 we explain their orbit) are these molecules and animals 

 and forces mere products of our fantasy, or are they just 

 as real as the gases and the animals the laws of which 

 they are led to explain ? Are theories merely explana- 

 tory, are they like the fairy tales by means of which our 

 ancestors explained to themselves the world about them, 

 are they like the tales we often tell to our children with 

 the same object of explanation, or are they truly solid 

 fact about the real things of the world ? 



That may seem a simple question to which a plain 

 answer, Yes or No, might be given; but in truth it 

 raises the most profound and abstruse problems of 

 philosophy and really lies without the scope of this book. 

 Our object is to discover what science is ; we have learnt 

 what laws and theories are, and what part they play in 

 science ; it is not directly part of our purpose to discuss 

 what value all this elaboration has when it is achieved. 

 But in a book of this kind it would be wrong to leave the 



