At the heart of much of Henry James’s fiction is the idea of an education—a gaining of knowledge by a protagonist that changes his or her view of the world. In the longer form of the novel, such as The Portrait of a Lady (1881), a number of experiences gradually educate the protagonist, but with the shorter form, such as in this story, James relies on one incident to change a character’s view of the world—and himself. The concept of “knowledge”—the key term in the title “The Tree of Knowledge”—is the central concern around which the psychological action revolves. Peter Brench, the protagonist, is a man who loses his innocence, his illusions, through an experience with his godson, Lancelot Mallow.

The action begins with the announcement by Lancelot’s mother, Mrs. Mallow, that her son shall not return to college at Cambridge, but instead will go to Paris and learn to become a painter. Peter, a family friend who has been secretly in love with Mrs. Mallow for twenty years, arranges a meeting with Lance in an attempt to persuade him not to go to Paris, but to return to college.

Peter does not wish Lance to go to Paris to study painting because he fears that Lance will learn that his father, who has proclaimed himself a great artist as a sculptor, and who has devoted his life to his sculpting, is without talent. Peter primarily wishes to protect Mrs. Mallow from this knowledge, for he fears that it would bring her great pain and destroy her love for her husband. When Lance questions Peter on why Peter does not wish him to go to Paris, Peter declares, “I’ve the misfortune to be omniscient.” Lance misinterprets the statement to mean that Peter does not believe that Lance has the talent to become an artist. Lance wishes to reassure Peter that he is mature enough to find out the truth about himself, and he replies that his “innocence” no longer needs protecting.

While Lance is in Paris, Peter continues to have Sunday dinner with the Mallows, and he observes the “fond illusion” of the Mallows when it appears that some of the sculpting finally will be sold, and Morgan will gain a reputation as an artist. Peter knows that Morgan will never really amount to anything as a sculptor, for he is without a proper sense of proportion, a necessary aspect of the art. However, because the Mallows are independently wealthy, there is no need for Morgan to become successful, and Peter believes that for the well-being of all concerned, including himself, the present arrangement is best left as it is.

When Lance does return the following year from Paris, he has discovered that he does not have the talent to become a painter, and he also has discovered the lack of value of his father’s work—the very knowledge Peter wished to conceal from him. Peter extracts a promise from Lance not to tell his parents the truth about his father. It is Peter’s greatest wish that the couple retain their illusion. Peter’s goal of protecting Mrs. Mallow from the truth is called into question by Lance’s next visit home from Paris. In the final scene of the story, Lance tells Peter of a heated argument with his father, who castigated Lance for not developing his painting. Lance tells Peter that his mother, in order to relieve Lance’s feelings, came to him after the argument, and Lance discovered that she had known the true value of her husband’s work all along.

On hearing this, Peter is dumbfounded. Lance realizes how very...