Solomon
Ecclesiastes 1:15BSB·traditional attribution

What is crooked cannot be straightened, and what is lacking cannot be counted.

Matthew Henry Presbyterian @wholebiblehenry

Solomon, having asserted in general that all is vanity, and having given some general proofs of it, now takes the most effectual method to evince the truth of it, 1. By his own experience; he tried them all, and found them vanity. 2.

Commenting on Ecclesiastes 1:12-18

John Gill Reformed Baptist @doctorgill

That which is crooked cannot be made straight,.... By all the art and cunning, wisdom and knowledge of man, that he can attain unto; whatever he, in the vanity of his mind, may find fault with in the works of God, either of nature of providence, and which he may call crooked, it is not in his power to make them straight, or to mend them; see Ecc 7:13.

Jamieson-Fausset-Brown Reformed @jfbcommentary

Investigation (Ecc 1:13) into human ways is vain labor, for they are hopelessly "crooked" and "cannot be made straight" by it (Ecc 7:13). God, the chief good, alone can do this (Isa 40:4; Isa 45:2). wanting-- (Dan 5:27). numbered--so as to make a complete number; so equivalent to "supplied" [MAURER]. Or, rather, man's state is utterly wanting; and that which is wholly defective cannot be numbered or calculated.