♈Mercury in Aries
Thinks fast and says it immediately. Associated with quick decisions, a low tolerance for long explanations, and an argumentative streak that is usually about pace rather than hostility. The traditional caution is speaking before the thought has finished forming.
♉Mercury in Taurus
Thinks slowly and thoroughly, and does not enjoy being rushed. Associated with a practical mind that wants a concrete example, retains what it learns for a long time, and is extremely difficult to argue out of a conclusion once it has been reached.
♊Mercury in Gemini
Mercury rules Gemini, so this is the mind unencumbered: fast, verbal, endlessly curious and easily bored. Associated with picking things up quickly, with talking in order to think, and with a scattered attention that gathers a great deal and files almost none of it.
♋Mercury in Cancer
Thinks by feel and remembers by association. Associated with an excellent memory for anything with emotion attached, with an indirect way of raising difficult subjects, and with real difficulty being objective about anything personal.
♌Mercury in Leo
Thinks in whole pictures and speaks with conviction. Associated with a flair for explaining things memorably, with opinions delivered as statements, and with a genuine dislike of being corrected in public.
♍Mercury in Virgo
Mercury rules and is exalted in Virgo, which happens nowhere else. This is the most precise mind in the zodiac: analytical, exact, excellent at editing, and inclined to mistake its own uncertainty for stupidity when it is usually evidence of care.
♎Mercury in Libra
Thinks comparatively, and rarely reaches a conclusion without having argued the other side first. Associated with fairness, diplomacy and good judgement, and with a genuine slowness to decide that other people mistake for evasion.
♏Mercury in Scorpio
Thinks investigatively and does not stop at the first answer. Associated with research, strategy and an instinct for what is being concealed, with the traditional caution being obsession: this mind does not put a subject down when it is finished with it.
♐Mercury in Sagittarius
Thinks in principles and large patterns, and is impatient with the small print. Associated with teaching, storytelling and genuine breadth, with the traditional caution being confident inaccuracy: the shape of the argument is right and the specifics were not checked.
♑Mercury in Capricorn
Thinks structurally and does not speak until it is sure. Associated with rigour, long concentration and excellent judgement about what is realistic, with the traditional caution being a slowness to voice an idea that is already better than most of the ones being said aloud.
♒Mercury in Aquarius
Thinks in systems and arrives at conclusions other people have not considered. Associated with originality, an interest in how things work and a stubborn independence of view, with the traditional caution being attachment to a position because it is one's own.
♓Mercury in Pisces
Thinks in images and impressions rather than in steps, and often cannot show the working. Associated with metaphor, intuition and creative thought, with the traditional caution being detail: dates, names and exactly what was said are the weak point.