This illiberality in religion was caused in the first place by the power of the clergy.  Religion was the essential feature of the Scotch war against Charles I. Theological interests dominated the secular because the clergy were the champions of the political movement.  Hence, in the seventeenth century, the clergy were enabled to extend and consolidate their own authority, partly by means of that great engine of tyranny, the kirk sessions, partly through the credulity which accepted their claims to miraculous interpositions in their favour.  To increase their own ascendancy, the clergy advanced monstrous doctrines concerning evil spirits and punishments in the next life; painted the Deity as cruel and jealous; discovered sinfulness hateful to God in the most harmless acts; punished the same with arbitrary and savage penalties; and so crushed out of Scotland all mirth and nearly all physical enjoyment.

Scottish literature of the eighteenth century failed to destroy this illiberality owing to the method of the Scotch philosophers.  The school which arose was in reaction against the dominant theological spirit; but its method was deductive not inductive.  Now, the inductive method, which ascends from experience to theory is anti-theological.  The deductive reasons down from theories whose validity is assumed; it is the method of theology itself.  In Scotland the theological spirit had taken such firm hold that the inductive method could not have obtained a hearing; whereas in England and France the inductive method has been generally followed.

The great secular philosophy of Scotland was initiated by Hutchinson.  His system of morals was based not on revealed principles, but on laws ascertainable by human intelligence; his positions were in fiat contradiction to those of the clergy.  But his method assumes intuitive faculties and intuitive knowledge.

The next and the greatest name is that of Adam Smith, whose works, “The Theory of Moral Sentiments” and “Wealth of Nations,” must be taken in conjunction.  In the first he works on the assumption that sympathy is the mainspring of human conduct.  In the “Wealth of Nations” the mainspring is selfishness.  The two are not contradictory, but complementary.  Of the second book it may be said that it is probably the most important which has ever been written, whether we consider the amount of original thought which it contains or its practical influence.

Beside Adam Smith stands David Hume.  An accomplished reasoner and a profound thinker, he lacked the invaluable quality of imagination.  This is the underlying defect of his history.  Important and novel as are Hume’s doctrines, his method was also deductive, and, like Adam Smith, he rests little on experience.  After these two, Reid was the most eminent among the purely speculative thinkers of Scotland, but he stands far below them both.  To Hume the spirit of inquiry and scepticism is essential; to Reid it is a danger.