With the death of David Foster Wallace, the author of “Infinite Jest,” who took his own life on Sept. 12, the world of contemporary American fiction lost its most intellectually ambitious writer. Like his peers Richard Powers and William T. Vollmann, Wallace wrote big, brainy novels that were encyclopedically packed with information and animated by arcane ideas. In nonfiction essays, he tackled a daunting range of highbrow topics, including lexicography, poststructuralist literary theory and the science, ethics and epistemology of lobster pain. He wrote a book on the history and philosophy of the mathematics of infinity. Even his signature stylistic device — the extensive use of footnotes and endnotes — was a kind of scholarly homage.

But Wallace was also wary of ideas. He was perpetually on guard against the ways in which abstract thinking (especially thinking about your own thinking) can draw you away from something more genuine and real. To read his acutely self-conscious, dialectically fevered writing was often to witness the agony of cognition: how the twists and turns of thought can both hold out the promise of true understanding and become a danger to it. Wallace was especially concerned that certain theoretical paradigms — the cerebral aestheticism of modernism, the clever trickery of postmodernism — too casually dispense with what he once called “the very old traditional human verities that have to do with spirituality and emotion and community.” He called for a more forthright, engaged treatment of these basic truths. Yet he himself attended to them with his own fractured, often-esoteric methods. It was a defining tension: the very conceptual tools with which he pursued life’s most desperate questions threatened to keep him forever at a distance from the connections he struggled to make.

Given his considerable intellectual gifts and large cult following, it may come as a surprise to learn that Wallace’s one formal, systematic contribution to the world of ideas was never published and remains almost completely unknown. This is his undergraduate honors thesis in philosophy — “Richard Taylor’s ‘Fatalism’ and the Semantics of Physical Modality” — which he submitted for a degree at Amherst College in 1985. Its obscurity is easy enough to understand. A highly specialized, 76-page work of semantics and metaphysics, it is not for the philosophically faint of heart. Brace yourself for a sample sentence: “Let Φ (a physical possibility structure) be a set of distinct but intersecting paths j i –j n , each of which is a set of functions, L’s, on ordered pairs {t, w} ({time, world situation}), such that for any L n , L m in some j i , L n R L m , where R is a primitive accessibility relation corresponding to physical possibility understood in terms of diachronic physical compatibility.” There are reasons that he’s better known for an essay about a boat.

For all its inscrutability, though, the thesis represents an important phase in Wallace’s development. Once its goals and ambitions are understood, the paper casts a revealing light on the early stages of his struggle to use the powers of his formidable mind for the higher good: to protect against the seductions of the intellect, and to find solid ground for his most urgent and heartfelt convictions.