The placement of Mercury in Capricorn indicates you have a need to function mentally within set structures and to achieve goals. Much of the behavior and many of the personality characteristics associated with Mercury in Capricorn are a result of your need for mental organization and a focus on the concrete and the realistic. Mercury is generally well placed in Capricorn. This is symbolized by the natural trine between Capricorn and Mercury-ruled Virgo. Capricorn is the Cardinal Earth sign. Capricorn’s active earth quality resonates with the concrete and objective energy inherent in Mercury and symbolically forces Mercury’s changeable airy energy to apply itself to practical matters and to run along organized grooves. 

Inherent in the placement of Mercury in Capricorn, however, is a tendency for spontaneity and freedom of thought to be sacrificed. The earth of Capricorn symbolically traps and confines Mercury’s airy energy. If you are not careful to keep the Mercury-associated functions stimulated, these can easily “get into a rut” and become rigid and stale. 

Insecurities

With Mercury in Capricorn, if you are insecure, then your mind is likely to be unsure of its own power of independent thinking. You will not really trust your mind or yourself to set proper goals for yourself. Therefore, you will rely on established conventions and these will govern your mind. In actuality, your ego has subconsciously set up this defense mechanism to keep the mind away from the Truth, which threatens the ego.  This insecurity about the mind, however, can also result in feelings of inferiority, mentally or with respect to your powers of communication. Your feelings of inferiority are likely to be exacerbated by the natural Capricornian drive to for success, which you do not think is within your reach. 

Mercury in the 5th House:

The placement of Mercury in the 5th House suggests the energy of a Mercury-Sun contact. Generally, your mental and communication functions are enlivened and energized in the 5th House. They are directed toward expressing your personality and your creativity and showing this to others. 

To do this, you must think about your persona and talents. Thus, you have an opportunity to consciously formulate (or modify) your personality traits or to develop your creative potential. Mercury in the 5th House may also signify that your positive attributes and creative energies are chiefly intellectual or involve communication skills. Even if you are expressive and creative in non-mental ways, you will probably apply thought to the organization of these functions. 

Having Mercury in the 5th House, you are also predisposed to apply your intellect to things having to do with.  You are apt to engage in mental play, too, meaning that you are likely to express your mental energies in a playful, rather than a rigid or overly serious manner. Secondly, you are likely to have a drive to communicate to others in a way which is self-expressive and displays your creativity. 

As an individual with Mercury in the 5th House, your communication style is likely to be lively and even playful. There may be much talk about things that involve creativity. However, you should guard against a tendency to use communication as a forum to focus attention on yourself (directly or through your children).