I am already sensible of decay in the power of walking, and find my memory not so faithful as it used to be. This may be partly owing to the incessant current of new matter flowing constantly through it; but I ascribe to years their share in it also.
Thomas JeffersonThe contradictory experiments of chemists leave us at liberty to conclude what we please. My conclusion is, that art has not yet invented sufficient aids to enable such subtle bodies [air, light, &c.] to make a well-defined impression on organs as blunt as ours; that it is laudable to encourage investigation but to hold back conclusion.
Thomas Jefferson