The acceptance of a theory as true does involve a personal choice in a way that a law does not. Different people do differ about theories; they can choose whether or no they will believe them; but people do not differ about laws; there is no personal choice; universal agreement can be forced. Again, if we look at the history of science, we shall find that the great advances in theory are more closely connected with the names of the great men than are the advances in law. Every important theory is associated with some man whose scientific work was notable apart from that theory; either he invented other important theories or in some way he did scientific work greatly above the average. On the other hand there are a good many well-known laws which are associated with the names of men who, apart from those particular laws, are practically unknown; they discovered one important law, but they have no claim to rank among the geniuses of science. That fact seems to indicate that a greater degree of genius is needed to invent true theories than to discover true laws.