[161] sense, education, and learning, as to secure us against all delusion in themselves; of such undoubted integrity as to place them beyond all suspicion of any design to deceive others; of such credit in the eyes of mankind as to have a great deal to lose in case of their being detected in any falsehood, and at the same time attesting facts performed in such a public manner as to render detection unavoidable —­all which circumstances are requisite to give us a full assurance in the testimony of men.

In the Dialogues on Natural Religion which were not published till after his death (1776), Hume made an attack on the “argument from design,” on which deists and Christians alike relied to prove the existence of a Deity.  The argument is that the world presents clear marks of design, endless adaptation of means to ends, which can only be explained as due to the deliberate plan of a powerful intelligence.  Hume disputes the inference on the ground that a mere intelligent being is not a sufficient cause to explain the effect.  For the argument must be that the system of the material world demands as a cause a corresponding system of interconnected ideas; but such a mental system would demand an explanation of its existence just as much as the material world; and thus we find ourselves

[162] committed to an endless series of causes.  But in any case, even if the argument held, it would prove only the existence of a Deity whose powers, though superior to man’s, might be very limited and whose workmanship might be very imperfect.  For this world may be very faulty, compared to a superior standard.  It may be the first rude experiment “of some infant Deity who afterwards abandoned it, ashamed of his lame performance”; or the work of some inferior Deity at which his superior would scoff; or the production of some old superannuated Deity which since his death has pursued an adventurous career from the first impulse which he gave it.  An argument which leaves such deities in the running is worse than useless for the purposes of Deism or of Christianity.

The sceptical philosophy of Hume had less influence on the general public than Gibbon’s Decline and Fall of the Roman Empire.  Of the numerous freethinking books that appeared in England in the eighteenth century, this is the only one which is still a widely read classic.  In what a lady friend of Dr. Johnson called “the two offensive chapters” (XV and XVI) the causes of the rise and success of Christianity are for the first time critically investigated as a simple historical phenomenon.  Like most freethinkers of the