The universe is merely a fleeting idea in God's mind - a pretty uncomfortable thought, particularly if you've just made a down payment on a house.

Allen’s line fuses metaphysical skepticism with everyday anxiety. The first clause echoes idealist theology—the notion that reality is contingent, perhaps only a thought in a divine mind—undercutting the solidity of the material world. The punchline (“particularly if you’ve just made a down payment on a house”) drags that abstraction into the realm of mortgages and sunk costs, exposing how human beings stake their lives on permanence: property, plans, and long-term security. The humor comes from the collision between cosmic impermanence and bourgeois practicality, a characteristic Allen move that turns existential dread into a joke while still leaving the dread intact.