The placement of Mercury in Taurus indicates you have a need for security in the mental environment. Very often, this sense of mental security derives from a knowledge of physical security. Much of the behavior and many of the personality characteristics associated with Mercury in Taurus are a result of this need to have a mental perception of safety and security. Therefore, it is often the case that the functions associated with Mercury are focused in their application on acquiring and retaining the elements of physical and material security. This diligent application tends to concentrate those functions and develop tenaciousness. 

Taurus is the Fixed Earth sign. Both the fixity and the earthiness of Taurus’ nature symbolically slow and entrap the quick and airy nature associated with Mercury. This is not entirely without benefit, as this forces these functions to concentrate, thus allowing them to fulfill their purpose. The benefit of the practical and concrete nature thus conferred is symbolized by the natural trine existing between Taurus and Mercury-ruled Virgo. Still, the fixed earth influence on Mercury can result in tension or a lack of optimization with respect to the Mercury-symbolized functions, as their natural proclivities are held back considerably. 

Insecurities

Having Mercury in Taurus, if you are insecure, your lack of mental quickness and ready mental grasp can easily cause you to lose your intellectual self-confidence. You are likely to compensate for this feeling of inferiority by taking satisfaction in your possessions.  Your mind is thoroughly attached to its activity of thinking about gain and loss.  This attachment keeps you from thinking about the real value of life, which is not in intellectual achievement. Of course, if you also lack possessions, you are likely to feel particularly insecure and those functions symbolized by Mercury will be constantly engaged in thinking about your physical and material welfare. 

Mercury in the 10th House:

Mercury in the 10th House suggests that you have a practical bent to your mental and communicating functions and also that you are mentally goal-oriented. You are not likely to dwell overly long on analysis. Instead, you will evaluate the data and reach a decision that can help you proceed toward your goal. The purpose of thought and communication, in your mind, is to get things done. 

As an individual with Mercury in the 10th House, from your point of view, thought, to be worth engaging in, should be useful and constructive. The mind should have a goal and then proceed forward to actualize that goal. Your mental energies are likely to be bent on accomplishment. 

If there is a danger associated with Mercury in the 10th House, it is that, in your eagerness to harness yourself to achieve success for yourself, you fail to deliberate sufficiently or to take seriously the nuances or logical contradictions that your mind brings to light (or that others communicate to you). To the extent that your mind is goal-focused and disciplined, it is likely to be strong, though not necessarily intellectual. With Mercury in the 10th House, if success eludes you, however, you may lose mental confidence. You will generally look for success in everyday accomplishments, however, and this should keep your mind positive and always occupied with something to achieve.