While Baron D'Holbach is normally considered a staunch advocate of atheism, I've found a few passages in The System of Nature which suggest he might have had a belief closer to Deism than atheism. The following passage certainly caught my eye:
"Of whatever nature this great Cause of causes may be, it is evident to the slightest reflection that he has been sedulous to conceal himself from our view; that he has rendered it impossible for us to have the least- acquaintance with him, except through the medium of nature, which he has unquestionably rendered competent to everything. This is the rich banquet spread before man; he is invited to partake, with a welcome he has no right to dispute; to enjoy that which must make him most acceptable; to be happy himself is to make others happy; to make others happy is to be virtuous, to be virtuous he must revere truth. To know what truth is, he must examine with caution, scrutinize with severity, every opinion he adopts.
This granted, is it at all consistent with the majesty of the Divinity, is it not insulting to such a being to clothe him with our wayward passions, to ascribe to him designs similar to our narrow view of things; to give him our filthy desires; to suppose' he can be guided by our finite conceptions: to bring him on a level with frail humanity, by investing him with our qualities, however much we may exaggerate them; to indulge an opinion that he can either act or think as we do; to imagine he can in any manner resemble such a feeble play-thing, as is the greatest, the most distinguished man? No! it is to degrade him in the eye of reason; to violate every regard for truth, to set moral decency at defiance; to fall back into the depth of Cimmerian darkness. Let man, therefore, sit down cheerfully, to the feast; let him contentedly partake of what he finds; but let him not worry the Divinity with his useless prayers, with his shallow-sighted requests, to solicit at his hands that which, if granted, would in all probability be the most injurious for himself: these supplications are, in fact, at once to say, that with our limited experience, with our slender knowledge, we better understand what is suitable to our condition, what is convenient to our welfare, than the mighty Cause of all causes who has left us in the hands of nature: it is to be presumptuous in the highest degree of presumption; it is impiously to endeavour to lift up a veil which it is evidently forbidden man to touch; that even his most strenuous efforts attempt in vain."
That, to me, sounds like a man that believes in a Deistic God that he knows he could never have any true "knowledge" of, and accepts his limitations.
