Which American artist is more deserving of a psychobiography than Thomas Eakins (1844-1916)? For practitioners of armchair diagnosis, the painter of the “Gross Clinic” offers endless fodder. He lost his position of chief instructor at the Pennsylvania Academy for the Fine Arts for removing the loincloth of a male model before a class of female students. His niece accused him of sexual assault and took her own life. A trove of photographs recently appeared showing, among other things, a nude Eakins posing with nude females other than Mrs. Eakins (who also appeared). Why, one asks, did a book like Henry Adams’s “Eakins Revealed” (Oxford University Press, 554 pages, $40) not appear a decade ago? And what, exactly, made Eakins tick?

The answer to both questions is Philadelphia. Because of its Quaker origins, Philadelphia was the most empirical of American cities, with the deepest disdain for theory and speculation. Since Quakers needed no ministers for their silent worship, they also needed no Harvards or Yales in which to train them. Instead, education in Philadelphia was a relentlessly practical affair. The city excelled in medicine, engineering , and applied science, leaving it to New England to groom the intelligentsia of America. The philanthropist Stephen Girard neatly summed up this attitude in 1831 with his curriculum for Girard College, whose pupils were to be taught “facts and things, rather than words and signs.”

This might be taken as the motto for Eakins, a scientific realist and an enthusiastic devotee of dissection. A preference for facts and things has also dominated the research on Eakins, which, not surprisingly, has been centered in Philadelphia. The most important work has been conducted by scholars at three Philadelphia institutions – the Pennsylvania Academy, the University of Pennsylvania, and the Philadelphia Museum of Art (which organized the authoritative 2001 exhibition) – all of whom has scrupulously avoided psychobiography. In this way, Eakins, though the most obvious of targets, was barely touched by the vogue for psychosexual conjecture.

Henry Adams’s new book more than makes up for this. It is fitting that this speculative book would be written by a product of the New England intellectual world, a man whose ancestor wrote the celebrated “Education of Henry Adams.” And this Mr. Adams aims high indeed. Since 1933, when Lloyd Goodrich published his hagiographic “Thomas Eakins: His Life and Work,” an “intense national pride and moralistic fervor” has afflicted all Eakins scholarship, Mr. Adams suggests, insulating him from serious criticism. Actions that might be questionable – such as the loincloth scandal – have been interpreted to Eakins’s benefit and as a sign of his uncompromising pursuit of artistic truth.

For Mr. Adams, though, there was always something in the artist’s work that could not be squared with the prevailing hero worship, something distinctly “brutal and unpleasant.” His sense that there was much more to the artist than the myth spurred this ambitious book, the first attempt to take the full measure of Eakins as a psychological being. The author does not mince words: The Eakins that emerges here is mentally disturbed to a crippling and even pathological extent, signs of which are to be found everywhere in his painting. For Mr. Adams, Eakins’s art cannot be understood at all unless it is recognized as the expression, at least in part, of his mental illness.

This is a tall order. Because of the discretion of Eakins’s era, there is very little written documentation, and even that is of the most oblique and ambiguous sort. The most serious and specific charges against Eakins, of indecent exposure and seduction, were made by two women who were attestably mentally ill. To fill in the gaps, Mr. Adams relies on the indirect evidence of the work itself, and here he goes astray.

The central thesis of “Eakins Revealed” is that the artist suffered from a strong sense of sexual confusion, which caused him to manipulate the features of his subjects so that his women looked mannish and his men womanish. Mr. Adams speculates that Eakins “imagined women as castrated or incomplete versions of men, and was at once disturbed and fascinated by the thought.” To find evidence for this, he reads paintings with a surprising literalness. For example, the brutal mastectomy operation in the “Agnew Clinic” (1889), one of Eakins’s most harrowing works, is an attempt to turn his hysterical mother “into something more similar to a man.”

Much of the evidence hinges on the way that the artist’s nudes are depicted from the rear, concealing their sexual parts. Thus one of the male youths cavorting in “Swimming” (c. 1884) has the “exaggerated, rounded buttocks” of a woman while the lithe female model in “William Rush Carving the Allegorical Figure of the Schuylkill River” (1875-77) “is a composite of male body parts that have been assembled to create a quasi-woman.” To depict a nude from the rear, however, is not necessarily a sign of sexual confusion, let alone a homosexual rape fantasy – as Mr. Adams writes – it is a standard Victorian convention of decorum. Here, as elsewhere, Mr. Adams’s debunking impulse causes him to read the evidence in the most damning way possible, and to then extrapolate further from his hypotheses.

The most egregious chain of suppositions is his argument that because Eakins’s mother was manic-depressive, she undressed herself inappropriately before him, and that this in turn gave him an addiction to voyeurism. But voyeurism is only one of the roster of diagnoses, and, in turn, the reader learns of Eakins’s exhibitionism; his possible homosexuality, manic depression, and obsessive compulsive disorder; his possible laudanum addiction; and – if that were not already enough – that he “suffered from a deficit of serotonin neuromodulation” and drank too much milk.

There is no question that Eakins was a man of enormous personal passions, whose sexual life was not straightforward, nor free from confusion and pain. But surely this is true of many an artist – and many a human being in general. It is perhaps possible – although arguable – that Eakins painted nudes because of a predatory and scarcely governable voyeurism, but it is more interesting to know why these nudes are so arresting and haunting, not as pathology but as art. Mr. Adams’s book assumes, in good Freudian fashion, that the secret of sexual identity is the key to all other secrets: Once it has been laid bare, a person has nothing left to hide. But Eakins’s central mystery is something else entirely. How is it that an artist who looks at nothing but observed fact – physical solids in space; the mechanical action of muscle groups and skeletal systems – should prove to be America’s most eloquent painter of emotion? And here, alas, Mr. Adams’s ambitious but flawed book is unfortunately silent.

Mr. Lewis is a professor of art at Williams College. His books include “Frank Furness: Architecture and the Violent Mind” and “The Gothic Revival.”