[In the following review, Gray offers favorable assessment of Mason and Dixon. According to Gray, Pynchon "transforms what might have been a merely amusing historical novel into a moving and profound meditation on the search for truth."]

Historians should not read Thomas Pynchon's 733-page novel, Mason and Dixon, for information about the book's main characters, Charles Mason and Jeremiah Dixon, the two English astronomers who spent five years (1763–1768) establishing the boundary between Maryland and Pennsylvania. For that, they will find most of what is known in the brief entries in the Dictionary of Scientific Biography. There are, however, other reasons to read Pynchon's bestseller. First, historians will find that, although Pynchon has a penchant for caricature—which yields a Jewish George Washington and a Benjamin Franklin who in ordinary conversation utters epigrams such a "strangers heed my wise advice,—never pay retail price"—the range and depth of the author's historical knowledge is astonishing. He has mastered both the particulars of eighteenth-century astronomy and the cultural history of colonial Pennsylvania. Scholars will also find that Pynchon's faux-Augustan prose, invented doggerel, and numerous madcap characters—including a talking dog and an exiled French master chef—lend Mason and Dixon the appealing feel of an eighteenth-century novel. Above all, historians should read Mason and Dixon because Pynchon approaches his characters and their world with rare compassion and seriousness. He transforms what might have been a merely amusing historical novel into a moving and profound meditation on the search for truth.

Pynchon has long been interested in the problem of certainty in a modern world whose boundaries in time and space are everywhere giving way to a vast and nebulous media-created reality. His protagonists, in their quest for certainty, often come upon alternate realities, shaped by dreams or hallucinations and freed from the disintegrative forces that make modern life alienating and dull. Before reaching the utopian realm, his protagonists must first recognize that their own reality is the result of dissimulation, duplicity, fakery, double-dealing, conspiracy, lying, cheating, cunning, and the paranormal—forces that, in Mason and Dixon, surface as conspiring Jesuits, Freemasons, illuminati, Kaballists, and Jacobites (of whom the older Mason tells the younger Dixon, "anyone who was seventeen that summer [of the '45] … was a Jacobite." In the America Pynchon writes about, things are not what they appear to be. If for characters in Pynchon's earlier novels this realization was something discovered, for the two protagonists of Mason and Dixon, it is taken fully for granted and also something that science somehow promises to overcome.

In addition to establishing the boundary line that bears their name, Mason and Dixon took part in the largest scientific undertaking of the eighteenth century: the tracking of the transit of Venus. The purpose of that project was to determine the distance between the sun and the earth—a result, participants hoped, that would permit the complete charting of the universe. Mason and his assistant Dixon, in their capacity as observers of the project, found themselves in Dutch South Africa, where Pynchon begins as account of their partnership. Born of an eighteenth-century belief that the universe is finest and fundamentally rational, their partnership rests on the assumption that the face of the earth can be comprehended through the careful application of universal, rational principles. None of this characterization is to suggest that Pynchon depicts Mason, Dixon, and their world as purveyors of mindless optimism. Instead, he implies a pervasive and melancholy sense that rational means may not yield rational ends. Hence the Reverend Wicks Cherrycoke, an alleged associate of Mason and Dixon and the narrator of Pynchon's story, says of the two astronomers's best known achievement.

Here at the northeast corner of Maryland, the Geometrickal Pilgrim may well wish to stand … at this purest of intersections mark'd so far upon America. Yet, Geomancer, beware,—if thy gaze but turn Eastward by an Eye-lash's Diameter, thou must view the notorious Wedge,—resulting from the failure of the Tangent Point to be exactly at this corner of Maryland, but rather some five miles south, creating a semi-cusp or Thom of that Length, and a doubtful ownership,—not so much claim'd by any one Province, as prize'd for its Ambiguity.—occupied by all whose Wish, hardly uncommon in this Era of fluid Identity, is not to reside anywhere.

Wrongly plotted, the Mason-Dixon line could produce some sort of mysterious nether world. Whatever one may think of such an assertion, it has the effect of elevating the work of two minor astronomers to the sublime.

In present times, one does not need an astronomer to establish a boundary line. We live on land covered with benchmarks, often indicated by small concrete or stone monuments. These marks correspond to points on an imaginary grid composed of an infinite number of lines of longitude and latitude. Mason and Dixon were among those who first transformed that grid from the imaginary to the material by looking to the only fully accurate benchmarks available to them: the stars. To be a surveyor in colonial America was thus to be in a place where locations and boundaries between property and people had as much to do with the movement of the heavens as with distances and divisions between points on the land. It was also, Pynchon believes, to be the forger of a nation. For Pynchon, America before Mason and Dixon, was a giant, grinding, and licentious place—a place of oceans, continents, peoples, and races; a place vast in its wealth, vast in its misery, vast in its desires, and vast in its distances; a place of mixing and mingling; a place of crooks and cretins; a place of little quaintness or quietude. It was, in short, a place whose bounds were few.

Pynchon knows that Mason and Dixon's Ahab-like struggle to impose just one boundary on America was ultimately in vain. He knows that the boundary, which was meant to end confusion and conflict in the eighteenth century, became the center of conflict—bloody, damning conflict—in the nineteenth. He does not, however, fall prey to crude portent. Instead, he relishes his protagonists' determination to struggle against forces that are everywhere and always making the universe chaotic and incomprehensible—a determination driven by certainty about the existence of ultimate truth and the idea that, if people could only grasp that truth, they would all be much, much happier.