A Who-wrote-it?

I found the following passage in a book at a garage sale. I bought the book for $1.

A Google search will quickly answer who wrote the book and the passage, but you might take a stab at it before doing the search.

Of all the systems of religion that ever were invented, there is none more derogatory to the Almighty, more unedifying to man, more repugnant to reason, and more contradictory in itself, than this thing called Christianity. Too absurd for belief, too impossible to convince, and too inconsistent for practice, it renders the heart torpid, or produces only atheists and fanatics. As an engine of power, it serves the purpose of despotism; and as a means of wealth, the avarice of priests; but so far as respects the good of man in general, it leads to nothing here or hereafter.