Without just or sufficient reason; groundless.

Without cause or reason.

having no justifying cause or reason; "a senseless, causeless murder"; "a causeless war that never had an aim"; "an apparently arbitrary and reasonless change"

having no cause or apparent cause; "a causeless miracle"; "fortuitous encounters--strange accidents of fortune"; "we cannot regard artistic invention as...uncaused and unrelated to the times"

1. Self-originating; uncreated.