The opposite of the past tense verb thought (assumed) could be "knew" and the adjective could be "known."
The opposite noun for thought (consideration) could be action.
I can see why the word thoughtless might seem to be an antonym for pensive, since a pensive person thinks a lot and a thoughtless person doesn't, however, thoughtlessness is really about irresponsibility, it is not really about thought in general. The opposite of thoughtless is thoughtful or responsible, not pensive. The opposite of pensive would be spontaneous, or glib.
The opposite of master is slave.
The opposite of think would usually be act.The opposite of think (believe) could be doubt.The opposite motivation from think (use intellect) would be to feel (use emotion).
The opposite of duty is freedom or choice.
The opposite of lofty is low or humble.
thought
Never did know but is is you... have you thought of that?
The closest word might be dismissed, as in 'I dismissed the thought'.The word 'deemed' does not have an opposite. It means 'judged' or 'thought' or 'considered', as in "I deemed it best to ignore his rudeness." There is no opposite to that type of word.
The opposite of ingredients is "finished product" or "dish."
According to Carl Jung, the principle of opposites is basically that every wish immediately suggests it's opposite. Thus, if I have a good thought, I cannot help but have a bad thought in contrast to that good thought.
The opposite of "deep", as in "deep water", is "shallow". If you mean "deep" in a metaphorical sense, such as a "deep thought", the opposite might also be "superficial".
I thought the opposite was true, that they are not popular!
Subtract the number you first thought of.
The opposite of mechanical (by machine) could be biological or natural.The opposite of mechanical (perfunctory, without thought) could be conscious, considered, or thoughtful.Where mechanical has the connotation automatic, the opposite would be manual.
An apprentice , usually a teenager, is an individual learning a trade. The opposite might be thought of as a skilled tradesman , or skilled craftsman.
A turn of thought is the intentional focus of one's thoughts. It is possible to direct thoughts intentionally toward or away from someone or something, and typically a turn of thought means to direct the thought in the opposite direction from which they were.
Love: Two minds without a single thought.