Do you have a citation for your claim that Sherman was "guided by voices in his head"?
That, of course, is an exaggeration. It is true that Sherman had some mental problems prior to the War.
Thomas Jackson's students nicknamed him "Crazy Tom" as well.
Sherman was widely dogged by newspaper accounts of the era, both in the North and the South, claiming that he was insane; his mother's family was mentally unstable; various governmental reports and letters, including one from Grant to Lincoln, allude to this fact; and then you have numerous, contemporary biographies that speculate as to what sort of condition was actually behind Sherman's well-documented mental difficulties ... such as narcissistic personality disorder, manic-depression, or what have you. I will be glad to provide you with a cite or two later this evening, but it seems that a simple Google search would turn up ample verification.