Necessary tensism is the thesis that necessarily tensism is true.
- Tensism holds if and only if everything that exists in some way, either existed, or exists presently, or will exist. (Definition)
Here is an argument that tensism is not a necessary truth. In all of the premises, "the present" and tensed expressions must be taken to narrow temporal scope. I take definitions to be necessary truths. I will use "exists*" as an abbreviation for "existed, exists presently or will exist".
- Two times are temporally related if and only if they are simultaneous or one is earlier than the other. (Definition)
- Necessarily, if x existed, then it existed at a time earlier than the present. (Premise)
- Necessarily, if x will exist, then it will exist at a time later than the present. (Premise)
- Necessarily, if x exists presently, then it exists at a time simultaneous with the present. (Premise)
- Necessarily, if x exists*, then x exists in some way. (Premise)
- It is possible for there to exist in some way an entity at a time not temporally related to the present. (Premise)
- Necessarily, if tensism holds and x exists in some way, then x exists in some way at a time temporally related to the present. (By (1)-(6))
- Possibly, tensism is false. (By (7) and (8))
Moreover, not only is it possible that tensism is false, but we are not in a position to know tensism to be true. For we are in no position to know that there are no parallel timelines, and if there are, then tensism is false.