Jamieson, Fausset and Brown on Jeremiah 10:8

8. altogether--rather, "all alike" [Maurer]. Even the so-called "wise" men (Jr 10:7) of the Gentiles are on a level with the brutes and "foolish," namely, because they connive at the popular idolatry (compare Ro 1:21-28). Therefore, in Daniel and Revelation, the world power is represented under a bestial form. Man divests himself of his true humanity, and sinks to the level of the brute, when he severs his connection with God (Psa 115:8; Jon 2:8).

stock is a doctrine of vanities--The stock (put for the worship of all idols whatever, made out of a stock) speaks for itself that the whole theory of idolatry is vanity (Is 44:9-11). Castalio translates, "the very wood itself confuting the vanity" (of the idol).