It is curious to read these "Letters on the Laws of Man's Nature and Development," of which Harriet Martineau and Mr. Atkinson are the joint authors. The simple joy with which they declare themselves the proud discoverers of this happy land of the unknowable is almost touching. All that we know, say they, is matter or its manifestation. "Mind is the product of the brain," and "the brain is not, as even some phrenologists have asserted, the instrument of the mind." The brain is the source of consciousness, will, reason. Man is "a creature of necessity." "It seems certain that mind, or the conditions essential to mind, is evolved from gray vesicular matter." "Nothing in nature indicates a future life." "Knowledge recognizes that nothing can be free, or by chance; no, not even God,--God is the substance of Law." Whereupon Miss Martineau inquires whether Mr. Atkinson, in speaking of God, did not merely use another name for Law. "We know nothing beyond law, do we?" asks this meek disciple, seeking for information. Mr. Atkinson replies that we must assume some fundamental principle "as a thing essential, though unknown; and it is this which I wrongly enough perhaps termed God." But if it is wrong to call this principle God, and if they know nothing else behind phenomena, why do they complain so bitterly at being charged with Atheism? And directly Mr. Atkinson asserts that "Philosophy finds no God in nature; no personal being or creator, nor sees the want of any." "A Creator after the likeness of man" he affirms to be "an impossibility." For, though he professes to know _nothing_ about God, he somehow contrives to know that God is _not_ what others believe him to be. Eternal sleep after death he professes to be the only hope of a wise man. The idea of free-will is so absurd that it "would make a Democritus fall on his back and roar with laughter." "Christianity is neither reasonable nor moral." Miss Martineau responds that "deep and sweet" is her repose in the conviction that "there is no theory of God, of an author of Nature, of an origin of the Universe, which is not utterly repugnant to my faculties; which is not (to my feelings) so irreverent as to make me blush, so misleading as to make me mourn." And thus do the apostle and the disciple go on, triumphantly proclaiming their own limitations to the end of the volume.