T. S. Eliot's "Burnt Norton" begins with a series of concise yet complex philosophical statements. These revolve around the nature of "time," a subject the poem underscores through constant repetition:
Time present and time past
Are both perhaps present in time future,
And time future contained in time past.
If all time is eternally present
All time is unredeemable.
Lines 1-3 suggest that the past and present might, in some mysterious way, survive into the future rather than vanishing altogether. They also suggest that the future might be "contained in" the past: that is, already somehow existent within the past and waiting to unfold. However, the speaker qualifies these statements with "perhaps," establishing a quality of ambiguity that will continue throughout the poem. (In Part V of the poem, the speaker will admit, in fact, that "Words" are frustratingly incapable of capturing time's essence, so that any attempt along these lines is provisional at best.)
Adding to the ambiguity, the phrase in line 4—"If all time is eternally present"—can be read in two virtually opposite ways. It could mean either "If past, present, and future coexist simultaneously" or "If there is nothing but the present" (i.e., if time is an endless succession of vanishing moments).
In terms of the poem's overall argument, the second reading makes more sense. Line 5 finishes the thought: if all time is eternally present, then "All time is unredeemable." The word "unredeemable" basically means "unsalvageable," but here it also has Christian connotations (in light of the poem's many Christian references and Eliot's later career as a Christian public intellectual). To "redeem" time would be to make it in some way eternal, just as Christ is said to grant eternal life to mortal people. So if there were nothing but the ever-vanishing present, there would be no way to escape the present (and thus escape mortality). Instead, these opening lines seem to imply, past, present, and future do coexist: what appears to be a one-way flow of time—a series of vanishing moments—is really circular and/or simultaneous. As a result, our seemingly mortal, vanishing lives are part of something eternal. (Well, "perhaps," anyway!)
It's worth noting, here, that Eliot prefaces the Four Quartets as a whole with two epigraphs from the ancient Greek philosopher Heraclitus, whose work is deeply concerned with the flux (flow) of time. These epigraphs are discussed in depth in the Devices and Context sections of this guide. In general, "Burnt Norton" riffs on the philosophy of Heraclitus, as well as the Christian thinker St. Augustine and others, while confronting ancient time-related questions from a modern perspective. (For example, What is time? How does it work? Is there such a thing as eternity?) As a 20th-century writer, Eliot also seems aware of the way early-20th-century physics (e.g., Einstein's theory of relativity) overthrew conventional ideas about time—although this poem does not adopt a strictly scientific perspective.