Definition of "all there"
adjective
(idiomatic) Mentally competent; not absent-minded or insane.
Quotations
A suspicion that “he was not all there,” and therefore “one of God’s bairns,” had insured him, during his long orphanage, the food, and clothes, and shelter, necessary for life; but no one had given him love.
1885, Amelia E. Barr, chapter 1, in Jan Vedder's Wife