Condillac's "Traité des sensations" was published about ten years after La Mettrie's "L'histoire naturelle de l'âme," and therefore it is probable that Condillac had read this work, and gained some ideas from it. Yet Condillac never mentions La Mettrie's name nor cites his doctrines. This omission may be accounted for by the fact that the works of La Mettrie had been so condemned that later philosophers wished to conceal the similarity of their doctrines to his. Whether the sensationalists were influenced by his teachings or not, there is such a profound likeness in their teachings, that La Mettrie may well be regarded as one of the first French sensationalists as well as one of the leading French materialists of the time. Condillac and La Mettrie agree that experience is the source of all knowledge. As Lange suggests, [44] La Mettrie's development of reason from the imagination may have suggested to Condillac the way to develop all the faculties from the soul. La Mettrie asserts that reason is but the sensitive soul contemplating its ideas, and that imagination plays all the rôles of the soul, while Condillac elaborates the same idea, and shows in great detail how all the faculties of the soul are but modifications of sensation. [45] Both La Mettrie and Condillac believe that there is no gulf between man and the lower animals; but this leads to a point of disagreement between the two philosophers, for Condillac absolutely denies that animals can be mere machines, [46] and we must suppose that he would the more ardently oppose the teaching that man is merely a complicated machine! Condillac finally, unlike La Mettrie, believes in the existence of God. A final point of contrast also concerns the theology of the two writers. La Mettrie insists that we can not be sure that there is any purpose in the world, while Condillac affirms that we can discern intelligence and design throughout the universe. [47] Like La Mettrie and Condillac, Helvetius teaches that all the faculties of the mind can be reduced to sensation. [48] Unlike La Mettrie, he specifically distinguishes the mind from the soul, and describes the mind as a later developed product of the soul or faculty of sensation. [49] This idea may have been suggested by La Mettrie's statement that reason is a modification of sensation. Helvetius, however, unlike La Mettrie, does not clearly decide that sensation is but a result of bodily conditions, and he admits that sensation may be a modification of a spiritual substance. [50] Moreover, he claims that climate and food have no effect on the mind, and that the superiority of the understanding is not dependent on the strength of the body and its organs. [51]