A speaker announces a "great rant" in defense of "what was truth," and in the very next breath calls that rant "an ingenuous sort of entertainment / without much cost." The poem is about the gap between feeling passionate about a principle and actually paying for it. The speaker seems to know that a loud defense of truth, delivered when truth is already spoken of in the past tense, may be nothing more than a performance.
The title and the second line play with the same three words. "What truth was" sounds like the topic of a lecture, a settled matter about something finished. "In defense of what was truth" shuffles the order, and the phrase now echoes the old question "what is truth?", with the verb pushed into the past. Truth is treated as something that has already slipped away, so the rant begins to sound like a eulogy delivered at full volume. Defending something that is already gone is a safe thing to do, because no one can prove you wrong and nothing is at risk.
The grammar of the poem enacts this deflation. The first couplet is a full sentence, and its word order is a little grand: "a great rant I give," with the object first and the verb trailing behind, like someone clearing their throat before a speech. "Give" is a telling verb, since it suggests a gift or a recital more than a conviction. "Great" works two ways. It means big, and it also has the self-satisfied ring of "that was a great story." The second couplet has no verb at all. It dangles from the first like an afterthought and simply renames the rant, so a sentence full of swagger is followed by a smaller, quieter fragment that takes the swagger apart. There is no punctuation and no capital letter, which gives the poem the feel of a note jotted down, and it ends without a full stop, as if the thought has been dropped rather than finished.
The word choice rewards close attention. "Ingenuous" is easily mistaken for "ingenious," but it means candid, innocent, even naive. That leaves a pleasing uncertainty about who is being naive: the speaker, the audience, or the entertainment itself. "Sort of" adds a shrug, a casual hedge that undercuts any claim to seriousness. The sound of the lines shifts too. The first stanza is almost entirely short, blunt words: "rant," "give," "truth." The second swells into the four-syllable "ingenuous" and "entertainment," padded and glossy like show business, before snapping back to the curt monosyllables of "without much cost." There is no rhyme, but a thread of n and t sounds runs through "rant," "defense," "ingenuous," "entertainment" and "cost," which binds the anger of the first stanza to the showmanship of the second.
The final phrase is the most ambiguous. Who isn't paying? The speaker risks nothing by ranting, and the listeners lose nothing by listening. A cheaper reading is that truth itself costs nothing to praise. The sharpest reading, though, is that a defense which costs nothing is hardly a defense at all, and the poem lets the reader reach that verdict without stating it.
The poem is significant because of the irony in its own form. It describes a great rant, yet it is anything but one: it is quiet, brief and understated, and it never raises its voice. In effect it criticizes loud, easy certainty by declining to imitate it. A reader today might hear in it a comment on arguing online, where outrage is plentiful and consequences are rare, but that is an interpretation the text invites rather than something it states. What the poem plainly offers is an unflattering self-portrait in a few lines, a speaker honest enough to admit that defending the truth can be a pleasant way to pass the time. It leaves readers to ask themselves when their own passionate arguments have been that kind of entertainment.