Full Idea
The obvious minimal truthmaker for the truth that 'it is possible that a unicorn exists' is combinatorial. The elements of the combination are all that is needed.
Gist of Idea
The truthmakers for possible unicorns are the elements in their combination
Source
David M. Armstrong (Truth and Truthmakers [2004], 07.5)
Book Reference
Armstrong,D.M.: 'Truth and Truthmakers' [CUP 2004], p.91
A Reaction
This seems to imply that there are no possibilities which are not combinations of what currently exists.
Related Idea
Idea 18385 Logical atomism builds on the simple properties, but are they the only possible properties? [Armstrong]