In the interpretation of a natal chart the planetary symbols of Jupiter and Saturn represent the two ends of a continuum. This continuum describes how we humans learn and psychologically grow through our lives.
Jupiter represents growth through opportunities, change and expansion. Saturn represents growth through hard work, focus and discipline. Jupiter is associated with good luck, generosity and freedom of movement; Saturn with the rewards, responsibilities and authority that come with maturity and experience. In old-style astrology Jupiter was considered the planet of good fortune, and was called the "Great Benefic." Saturn was considered the planet of loss and bad luck and was called the "Great Malefic." Transits of Jupiter were considered fortuitous, while transits of Saturn were considered portents of ill fortune.
Many still think in terms of Jupiter as primarily a "good" planet and Saturn as a "difficult" planet. Individuals with a strong Jupiter are considered luckier and to have an easier life than those with a poorly aspected or weak Jupiter. Charts featuring conjunctions, squares and oppositions to Saturn may be considered to predict more difficult lives.
Circumstances seem to support this perspective. It is often true that individuals with a favorably aspected Jupiter do have an easier time in life, while those with a difficult Saturn work harder with less obvious rewards. But this is not always the case - an opposite result can occur. The strongly Jupiterian individual can fall prey to excess - too much of a good thing. Those with Jupiter tightly aspected to the inner planets may contend with obesity, substance abuse or excessive mental stress. Conversely, those with a similarly aspected Saturn may, through hard work and discipline, produce substantial results in their lives.
How, then, is one to understand the potential expression of these two forces within a natal chart?
Most of us have encountered the question, regarding a glass of water, "Is it half-full or half-empty?" The answer given is used to illustrate an optimistic or pessimistic attitude toward life - the optimist sees the glass as half-full, while the pessimist sees it as half-empty. The placement of Jupiter and Saturn in a birth chart provides an astrological measure of an individual's essential attitude toward life, and his or her natural tendency toward optimism or pessimism.
It must be emphasized that these are attitudes - expectations that may or may not be true in experience. Attitude does affect outcome, however, particularly when performance is involved. Most of us have had experiences where it seemed that our expectation of a particular outcome operated as a sort of self-fulfilling prophecy. We expected to succeed or fail, and we did. Our attitude toward ourselves and our corresponding expectations of life and its rewards plays a large role in what we ultimately reap out of life.
When it comes to Jupiter and Saturn - attitude is integral. The strongly Jupiterian individual expects success in their life and so often receives it. The strongly Saturnian individual expects difficulty in their life - and often receives it. This does not mean that the Jupiterian does not encounter difficulty, nor that the Saturnian does not encounter success. The roads to these outcomes are, however, quite different.
In reality we need a balance between Jupiter and Saturn. The forces of expansion and contraction are natural growth processes, often described in psychological theory. The famed psychologist Jean Piaget put forth a theory of learning that can be applied to an understanding of Jupiter and Saturn. According to Piaget, our natural desire is to maintain a state of balance within ourselves, to which he applied the biological term of "homeostasis." When new information comes our way an imbalance is created while we try to understand the new material. A type of internal struggle takes place while we assimilate the new information into our existing understanding. This struggle feels uncomfortable. We do not like it and actively work to reach a new internal balance. Piaget applied his learning theory to children, although it can be viewed as a model of the way we cope with new information throughout our lives.
The experience of new information coming in to disrupt our mental "homeostasis" can be equated with Jupiter. Jupiter is expansion and new opportunities. We all need new experience to move forward in our lives. We also need to assimilate that experience into a larger comprehension. We need Saturn - the principle of contraction - to help us integrate new information into our existing perspective.
Examining the interplay of Jupiter and Saturn within a chart can reveal an individual's ability to take advantage of the opportunities that come along in life. The Saturnian's tendency to see life as a difficult and burdensome process can lead to resistance to Jupiterian expansion. They can get stuck in a rut, plodding along hopelessly day after day. The over-blown Jupiterian can cartwheel from one expanding event to another without taking the time to learn from their experience. Neither individual is able to actively open to new growth. The Saturnian needs to consciously activate Jupiter - to open up to the opportunity of expansion. The excessive Jupiterian needs to invoke the Saturnian forces of discipline and focus to help them ground experience into earth reality. Only with a healthy interplay of these two forces for change can the individual actively grow throughout life.