Participial nominalization
The participial nominalization of a sentence is a noun phrase describing the state of affairs reported by the sentence. The main noun of the noun phrase is the participial form of the main verb of the sentence in simple sentences. Thus the participial nominalization of "Socrates is sitting" is "Socrates' being seated." It is harder to form the participial nominalization of a complex sentence such as "If Jones is a woman, then Jones is human", and one typically resorts to "Its being the case that" constructions: "Its being the case that if Jones is a woman, then Jones is human."
What the referrents of participial nominalizations of true sentences are and whether they are entities that exist is a deep philosophical question. See truthmaker.