James delivered these as the Gifford Lectures at Edinburgh across 1901 and 1902, in poor health, and they are the most readable book of philosophy anybody wrote in that period. The subject is religion and the method is unusual enough to be the whole point: he studies it by reading what individual people report about their own experience, and declines throughout to rule on whether any of it is true.

What reading it is like

Twenty lectures, around 500 pages, and it moves. James quotes at length from conversion narratives, diaries, letters from correspondents, and devotional literature, and the quotations are not illustration — they are the evidence and they carry the book.

It can be read out of order without much loss, and the lectures do different things. The sick soul and the divided self (VI–VIII) are the best writing and the ones people return to. Conversion (IX–X) is the most methodologically interesting. Saintliness (XI–XIII) is the longest stretch and the slowest. Mysticism (XVI–XVII) is the most quoted. The Conclusions and the Postscript are where he finally says what he thinks, and a reader who wants the argument rather than the material can start there and work backward.

The prose is the reason it survived. He was writing for an audience that had come to hear a course of lectures, and it shows.

The method, which is the claim

He studies religion through individuals rather than institutions, and through experience rather than doctrine.

The move is defended at the start and it is doing a lot. Institutional religion, he says, is second-hand — a set of habits acquired from other people. What he wants is the first-hand case: people for whom something happened. So the subject of the book is the extreme rather than the typical, and he says so, on the grounds that a phenomenon is best studied where it is most pronounced.

He also brackets the question of truth, deliberately and repeatedly. Whether anyone's experience was of God is not what the book is about. What it is about is what people report, how the reports sort, and what difference the experiences make to the lives that follow — which is the pragmatic maxim applied to a subject nobody had applied it to.

The typology

Two temperaments, which is the distinction that outlasted the book.

The healthy-minded are constitutionally disposed to see good. Evil is an aberration, or a mistake, or a thing to be looked away from. Their religion is optimistic, their conversion is gradual if it happens at all, and James is gently unimpressed.

The sick soul cannot do this. They have seen something — mortality, or cruelty, or their own condition — that will not be reasoned away, and any religion that is going to work for them has to pass through it rather than around it. James is plainly one of them, and the passages describing the condition are the closest he comes to writing about himself.

Out of this comes the divided self and its resolution, which is his account of conversion: a self at war with itself, and an event in which the center of energy shifts. He treats it as a natural process, describes subconscious incubation as its mechanism, and notes that the same structure appears in conversions to causes that have nothing to do with religion.

Key passages

Lecture I — the method: religion studied through individual experience rather than institutions.

Lectures IV–V — the religion of healthy-mindedness.

Lectures VI–VII — the sick soul; the anonymous account of a panic terror that James later admitted was his own.

Lecture VIII — the divided self.

Lectures IX–X — conversion, and the subconscious as its mechanism.

Lectures XVI–XVII — mysticism, and the four marks of a mystical state: ineffability, noetic quality, transiency, passivity.

Lecture XX and Postscript — the conclusions, and the "piecemeal supernaturalism" he finally commits to.

What is contested

That the focus on the extreme distorts the subject. By studying the most pronounced cases James gets vivid material and arguably the wrong population. Most religious life is communal, habitual and undramatic, and a study constructed to exclude it may be describing something other than religion.

That bracketing truth cannot be sustained. The pragmatic conclusion — that the fruits of the experience are what matters for assessing it — does quietly settle something, because it makes the value of a belief its credential. That is the objection Russell pressed against James generally, and it has a sharp form here.

That the individualism is a Protestant assumption rather than a finding. Treating institutions as second-hand and private experience as primary is a substantive theological position, and it is built into the design before any evidence is gathered.

That the psychology has aged. The subconscious mechanism he proposes for conversion belongs to a moment in the history of psychology that has passed. The descriptions have outlasted the explanation, which is the usual fate of good phenomenology attached to a theory.