When information is needed about the sphere of interests and intellectual capabilities of a person, then astrologers consider Mercury and the 3rd house of the horoscope. If these factors are combined in the birth chart, that is, Mercury is located in the 3rd house, then we can conclude about a person's good learning ability, his attentiveness and curiosity. Read more
MERCURY IN THE THIRD HOUSE and well-aspected has wonderful influence on the mental qualities of the native. It makes the mind serene and optimistic, inclined to study and research work. It gives fluency as a speaker and success by short journeys or travel and makes the relations of the person harmonious with his brothers. When Mercury is afflicted in the Third House it inclines to worry and pessimism, trouble and annoyance with sisters and brothers and when on short journeys.
Max Heindel
Your mental and communicative abilities will largely be applied to gaining superior intellectual ability, through education, travel and philosophical debate. An original thinker with much mental agility you excel in speaking, writing and communicating generally. This is a strong placing for Mercury and if mental power is directed to defined objectives then much success can be attained in any chosen direction.