James 1:8 (ESV),
he is a double-minded man, unstable in all his ways.
Here "double-minded" is a translation of δίψυχος, a compound of δίς, meaning "twice" (from δύο, the number "2") and ψυχή, referring to "soul".
The word seems to indicate someone who is two-souled, not in a literal sense of actually having two different souls in one body, but of a soul that is divided into two pieces, or somehow otherwise broken, if you will.
From HELPS Word Study:
1374 dípsyxos (an adjective, derived from 1364 /dís, "two" and 5590 /psyxḗ, "soul") – properly, "two souled"; (figuratively) "double-minded," i.e. a person "split in half," vacillating like a "spiritual schizophrenic." This term may have been coined in the NT (R. Lenski, P. Davids).
This reminds me somewhat of bipolar mood disorder, and I am wondering if it would be acceptable to understand James' use of δίψυχος in such a way.