unwise, rash, impulsive.

mindless, inane, illogical, blank, fatuous, thoughtless, vacant, empty-headed, brainless, heedless, unthoughtful, careless, unreasonable, rude, unoccupied, vacuous.

uncaring, unaffectionate, detached, unobservant, thoughtless, careless, unthoughtful, courtesy, unthinkingly, unmindful, unconcerned, hasty, inattentive, lumpen, impetuous, feckless, heedless, disregardful, unheeding, foolish, unreflective, reckless, stupid, forgetful, inconsiderate, undiscriminating, shallow, lumpish, irresponsible, careful, ill-considered, thoughtlessly.

There are no classes such as you have in mind in the Church, even though a few unthinking members seem to imply it by their actions; but there is no real class distinction in the Church of Jesus Christ of Latter- day Saints, only such that are based on the doing of the right and the wrong. - "Dorian", Nephi Anderson.

But still, there's a gulf between extreme probability and absolute certainty that's a bit wider than the unthinking reckon for. - "Ravensdene Court", J. S. (Joseph Smith) Fletcher.

Nominally, that is to say in the eyes of unthinking men, the North will conquer the South; but your existing armies will not do it. - "Who Goes There?", Blackwood Ketcham Benson.

unthinkingly, untiring, untempting, unthankful, untangling, unthinkable, unthinkably, untrusting.