The earlier work I read by Edward Conze was a history of the spread of Buddhism. Intentionally or not, that work pointed out how the faith has not been as devoid of the blood and oppression associated with other religions as some western orientalists, or indeed some Buddhists, would lead us to believe. This work, however, focuses on elucidating the undeniably impressive and, at times, beautiful system of thought that constitutes what seems to western observers as the most philosophical of all the world's major religions.
First off, Conze makes clear that Buddhism is not, in fact, philosophical. The sense that a western reader has of finding syllogistic argumentation in ancient Buddhist texts is a rationalization of the western mind, out to digest a foreign concept of thought in its own terms. Having said that, as one who has studied western philosophy, I am the first to admit that I interpreted Conze's survey of this thought as philosophy, and I often found striking analogies to many western thinkers, particularly those from the last 150 or so years. Indeed, to impose philosophical language on Buddhism, I would say that many of its schools could be said to be anti-philosophical, which is why, read as philosophy, they sometimes seem so contemporary.
As with existentialism, Buddhism imagines the human individual as inherently possessed of angst, whether they are conscious of it or not. (Buddhism is perhaps the earliest line of thought to posit an unconscious. Many ancient writings describe the ways that most people rationalize away their own suffering and those of other people.) People understand that they are alive as individuals, but also know that their existence is constantly slipping away and death is ever getting closer. Soon, being will give way to nothingness. The purpose of thought, from a Buddhist perspective, is to both confront and ease this angst.
Perhaps the foundational claim of Buddhist thought is that the self, as a force that unites and transcends individual experience, is an invention, a rationalization on the part of a feeble consciousness unable to cope with the excess of being- body(ies), feelings, perceptions, emotions and intentions. This sounds a lot like Jacques Lacan and those late twentieth-century thinkers that were influenced by him. The difference is that the Buddhist has faith that consciousness can eventually be purged of the misconception that is individuality. A Lacanian would say that human consciousness simply is this misconception, but the purpose of psychoanalysis in Lacanian thought is not so different from that of meditation in Buddhism. Neither the Buddhist nor the Lacanian mind convinces itself that the mind will literally dissolve itself in the living world. Rather, proper reflection can give one a sense of the inevitability of the delusion of self, and thus to take its challenges, indeed its passing into death, less seriously.
The mercilessly pragmatic nature of much Buddhist thought for centuries rejected any notion of creationism or even of questions of the nature of the universe (until relatively late in its history when, confronted and competing with various other religions, certain schools developed convoluted cosmologies and mythologies). Much as with the Wittgenstein of the Tractatus, the point of thinking is not to explain the world but to embrace the inexpressibly mystical element, which for the Buddhist is the affirmational void known as Nirvana.
The notion of an affirmational void, a negation, suggests a boundlessness to being. Everything is nothing and nothing is everything. The Truth is that truth is false and vice-versa. This collapsing of binaries is reminiscent of the radical dialectics of Derridean deconstruction.
This is not to say that such concepts concerned the average Buddhist for most of the religion's history. Indeed, if Buddhism was, in its earliest manifestations, unapologetically elitist, concerned only with and for the well-being of the intellectual-ascetic, its practitioners gradually came more and more to depend first on the gifts of kings and then on those of the masses. The laity was taught that if they renounced self-hood, such as giving their goods to the monks, the monks would magically protect them and grant the common people good luck. Yet, in their need for the graces of the masses, the monks did make themselves genuinely useful to the masses- providing education and, in theocratic settings, law and order.
Perhaps the appeal of Buddhism for most of its common followers was to seek self-negation as an instrument of self-interest. But this is only the inversion of the monk's impulse to seek the wisdom to understand that human existence amounts to nothing, yet also the compassion to care about humanity's well-being anyway.