The essay begins by discussing the role of literary criticism in England and Europe, as well as its importance to understanding poetry. Eliot describes how the English regard literary criticism with reluctance, whereas the French tend to embrace it. He argues that literary criticism is an important part of appreciating literature:

We might remind ourselves that criticism is as inevitable as breathing, and that we should be none the worse for articulating what passes in our minds when we read a book and feel an emotion about it, for criticizing our own minds in their work of criticism.

The essay then points out that in contemporary poetry, readers and critics tend to value what is new and personal, rather than what is “inherited” from the tradition:

We dwell with satisfaction upon the poet’s difference from his predecessors, especially his immediate predecessors.

Eliot argues against this tendency:

Tradition is a matter of much wider significance. It cannot be inherited, and if you want it you must obtain it by great labour. . . . This historical sense, which is a sense of the timeless as well as of the temporal and of the timeless and of the temporal together, is what makes a writer traditional. And it is at the same time what makes a writer most acutely conscious of his place in time, of his contemporaneity.

That is, it is a knowledge and understanding of tradition along with a development from that place of understanding that makes modern poetry great. In Eliot’s view, a poet’s essential education may deviate from her schooling, but it nevertheless must not be neglected. Essentially, poets need not excel in other subjects so long as they are well-read:

Some can absorb knowledge, the more tardy must sweat for it. Shakespeare acquired more essential history from Plutarch than most men could from the whole British Museum.

Unlike, for example, the Romantics, whose focus was on portraying individual emotional experience, Eliot insists that what is necessary for poetry is the combination of subjectivity with knowledge of history and literary tradition. Rather than reading and reacting to the individual writer alone, it is necessary, he says, to consider the writer’s place within the tradition and their interaction with existing literature:

No poet, no artist of any art, has his complete meaning alone. His significance, his appreciation is the appreciation of his relation to the dead poets and artists. You cannot value him alone.

A key analogy Eliot makes is that of the catalyst; in doing so, he brings scientific vocabulary and contemporary knowledge into the consideration of literature. Eliot argues that the mature poet acts as a sort of catalyst in terms of how he uses emotion and experience in his poetry:

When the two gases previously mentioned are mixed in the presence of a filament of platinum, they form sulphurous acid. This combination takes place only if the platinum is present; nevertheless the newly formed acid contains no trace of platinum, and the platinum itself is apparently unaffected; has remained inert, neutral, and unchanged. The mind of the poet is the shred of platinum. It may partly or exclusively operate upon the experience of the man himself; but, the more perfect the artist, the more completely separate in him will be the man who suffers and the mind which creates; the more perfectly will the mind digest and transmute the passions which are its material.

Just as the filament of platinum acts as a catalyst for the creation of sulphurous acid, so too does the poet’s mind act as a medium through which art is created. However,...