The Ninth House is the house of philosophy, religion, higher education, and long-distance travel. It describes your search for meaning, your relationship with faith and belief, and your experience of foreign cultures and distant lands. It is the house of the higher mind, as distinct from the everyday mental function of the Third House.
In traditional astrology, the Ninth House is called the House of Religion (or Long Journeys). It describes your spiritual beliefs, your relationship with religious institutions, and your experience of travel and foreign cultures.
A planet in the Ninth House describes how you seek meaning and growth. Jupiter in the Ninth House is at home, giving a natural faith, a love of travel and learning, and a generous, optimistic approach to life. Mercury in the Ninth House gives a philosophical mind, a curiosity about other cultures and belief systems. Saturn in the Ninth House may indicate a struggle with faith, or a serious, disciplined approach to philosophy and religion.
The Ninth House is naturally associated with Sagittarius and Jupiter: the sign of the seeker and the planet of faith. When planets are placed in the Ninth House, they take on something of this Sagittarian quality, becoming more expansive, more philosophical, more focused on the big picture.