Following Locke, he turned from speculation to experience and thus entered the path of criticism. Thus the material for all our ideas is derived from impressions. Moral necessity is of the same nature as physical necessity, although the operation of motives is extremely subtle and perhaps impossible completely to trace. Goodness is necessary to the good man and in the highest degree to God.
Immortality appears to have been left an open question.
Neither the idea of immaterial substance nor the doctrine of personal identity, neither the nature of divine justice nor the incompatibility of the noble powers of man with the swift span of earthly existence proves that the soul survives death. He traces the idea of cause neither to external objects, nor to reflection, nor to the senses, but to an experience of unvarying succession or custom. This idea, which has exerted a profound influence on later thought, was completed 'by Kant, who showed the nature of the necessity which the human mind has associated with causality. On the subject of theism Hume finds no sure footing. Neither cosmology, nor teleology, nor the moral argument is adequate as a ground of belief in God.