The placement of Mercury in Aries indicates you have a need for mental self-assurance. Very often, the tentative mental apparatus that you possess needs to be reinforced by a heavy dose of assertiveness. Much of the behavior and many of the personality characteristics associated with Mercury in Aries are a result of this need to be mentally confident. Being able to turn your thoughts and words into action may also provide self-confidence. 

Mercury is generally well-placed in Aries. Aries is the Cardinal Fire sign. The active fiery nature of Aries symbolically harmonizes well with the quick and airy nature of Mercury. Thus, the Mercury-associated functions are stimulated and activated. There is a danger, however, that Mercury’s mental energy could be overwhelmed by Aries’ need to act, resulting in mental impulsiveness and lack of self-control. This danger is symbolized by the natural quincunx between Aries and Mercury-ruled Virgo. 

Insecurities

With Mercury in Aries, mental insecurity stems from a subconscious realization that the mind is treading on new and uncharted round. It must keep up its confidence despite its lack of experience. This need to keep from giving into insecurity and maintain self-assertion often leads to mental bravado or recklessness, as the ego needs to prove itself. This mental insecurity can also manifest in your having such a need to prove yourself mentally that you are overly aggressive and argumentative. 

Mercury in the 8th House:

Mercury in the 8th House is a somewhat challenging placement for the planet because of the 8th House’s association with privacy. Even though public communication may be difficult for you, Mercury in the 8th House suggests a variety of strengths. These strengths can be developed once you realize that developing your mental and communication faculties is possible once these are turned in the right direction. 

As an individual with Mercury in the 8th House, while you may experience some difficulty with abstract or objective forms of mental activity, you are likely to become adept at cognitively understanding emotions and the motivations of others. Rather than perceiving by deduction, you are more likely to turn your mental attention to those matters where a more intuitive perception is valuable. Generally, with Mercury in the 8th House, you are most comfortable mentally when dealing with private or internal matters. 

Having Mercury in the 8th House, although your mind’s intuitive functions may be highly developed, this may not be evident to others because you may not display your mental or communicative aptitudes. You are likely to be interested in things that are secret and enjoy thinking about intimate details. You can be highly observant of nuances and personal details that others may overlook. For this reason, you are often an excellent judge of character and able to predict how people will act and react.