Full Idea
There is, in addition to the external world of physical objects and the internal world of ideas, a third realm of non-spatio-temporal objective objects, among which are thoughts.
Gist of Idea
There exists a realm, beyond objects and ideas, of non-spatio-temporal thoughts
Source
report of Gottlob Frege (The Thought: a Logical Enquiry [1918]) by Joan Weiner - Frege Ch.7
Book Reference
Weiner,Joan: 'Frege' [OUP 1999], p.129
A Reaction
This seems to be Platonism, and, in particular, to give a Platonic existent status to propositions. Personally I believe in propositions, but as glimpses of how our brains actually work, not as mystical objects.