The Writings of Thomas Jefferson. Vol. VII

281-2: (From 1823 letter to John Adams:) "The argument which they rest on as triumphant and unanswerable is that, in every hypothesis of Cosmogony you must admit an eternal pre-existence of something; and according to the rule of sound philosophy, you are never to employ two principles to solve a difficulty when one will suffice. They say then that it is more simple to believe at once in the eternal pre-existence of the world, as it is now going on, and may for ever go on by the principle of reproduction which we see and witness, than to believe in the eternal pre-existence of an ulterior cause, or Creator of the world, a being whom we see not, and know not, of whose form substance and mode or place of existence, or of action no sense informs us, no power of the mind enables us to delineate or comprehend. On the contrary I hold (without appeal to revelation) that when we take a view of the Universe, in its parts general or particular, it is impossible for the human mind not to perceive and feel a conviction of design, consummate skill, and indefinite power in every atom of it’s composition. The movements of the heavenly bodies, so exactly held in their course by the balance of centrifugal and centripetal forces, the structure of our earth itself, with it’s distribution of lands, waters and atmosphere, animal and vegetable bodies, examined in all their minutest particles, insects mere atoms of life, yet as perfectly organised as man or mammoth, the mineral substances, their generation and uses, it is impossible, I say, for the human mind not to believe that there is , in all this, design, cause and effect, up to an ultimate cause, a fabricator of all things from matter and motion, their preserver and regulator while permitted to exist in their present forms, and their regenerator into new and other forms. We see, too, evident proofs of the necessity of a superintending power to maintain the Universe in it’s course and order. stars, well known, have disappeared, new ones have come into view, comets, in their incalculable courses, may run foul of suns and planets and require renovation under other laws; certain races of animals are become extinct; and were there no restoring power, all existences might extinguish successively, one by one, until all should be reduced to a shapeless chaos. So irresistible are these evidences of an intelligent and powerful Agent that, of the infinite numbers of men who have existed thro’ all time, they have believed, in the proportion of a million at least to Unit, in the hypothesis of an eternal pre-existence of a creator, rather than in that of a self-existent Universe."
Jefferson concedes extinction of species, which he had previously denied, but affirms overall Design in refuting doctrine of eternalism.