The poem opens with a big, almost philosophical question: what kind of vision, or worldview, do "we" have? The title, "Weltanschauung," is the German word for exactly that. But the answer is strikingly small. Instead of ideals or beliefs, we get "my security / and a pint of wine." The grand question shrinks to personal safety and a little drink.
The last line, "This castle for greed," is the sharpest. A castle suggests protection, walls and wealth, and the poem seems to link that image to greed. Judging by the tone, the speaker is mocking, or perhaps confessing, how self-interest passes for a way of seeing the world. Notice the slide from "ours" to "my": the shared vision turns out to be private.
The mood is dry, clipped and quietly accusing. With so few words, the poem leaves a bare, uncomfortable feeling, as if the speaker has caught themselves, and the rest of us, being comfortable and a bit smug.