Mercury in Capricorn
In Capricorn, Mercury produces a mind that is clear, sometimes rigid and narrow, and always cautious and resourceful. Your thinking is methodical and careful. You know how to take things a step at a time, each fact building on the thought that went before. Your speech is organized and follows a logical and orderly pattern suggesting that you carefully examine and edit your words before they come out. You hardly ever say something that you are sorry for later.
You are not a quick learner, but you are one who never forgets what has been absorbed. You have an excellent memory and attention to the business at hand; a down-to-earth and practical thinker. Insecure about your mental abilities, you work hard to develop yourself with education and experience opportunities. You may be a bit defensive about your lack of education, that is the case. A special need to prove yourself, one way or another, is often the case with Mercury in Capricorn.

You have such very good powers of concentration, dignity, and an earnestness that can make you seem too serious. You can have a tendency toward moodiness and sulking, and you may have to work at showing any spirit of optimism. This placement of Mercury, especially if your Sun is also in Capricorn, produces one who is very quiet. Even if your Sun is in the more communicative Sagittarius or Aquarius, a Capricorn Mercury is not very talkative and sociable. You are especially self-conscience about speaking to strangers.

You have a very down-to-earth approach to thinking and communicating. Planning and organizing are you special strengths, and they carry you far in business and professional life. You do particularly well on long, drawn out projects that require perseverance and determination. Once you put your mind to a task, it will surely be completed and done well.

Cautious and skeptical, you may be conservative to a fault. Your love of tradition, and a natural pessimism, makes you slow to change patterns and premises that have worked in the past. Ideas that shake long-held beliefs are not very often accepted.