"[T]he portrait [of Benjamin Franklin] was commissioned by Robert Alexander, of the firm of William Alexander & Sons, Edinburgh. . . . The impressive beribboned document held by Franklin in the portrait is not a treaty or an Act of Parliament, but one of Alexander's deeds! The other books and pamphlets suggest the learned evidence brought in support of a wise man's decision. . . . [T]he bust of Isaac Newton, whose gaze is directed toward Franklin, invokes the greatest English voice of Reason. . . .
"[T]he portrait nonetheless sits squarely in the broader tradition of Enlightenment . . . . The pressure of the thumb against the chin . . . expresses the pressure of concentrated thought (the painting has sometimes been called the 'thumb portrait'), and the refracted light of Franklin's spectacles on his cheek furthers the effect."