Where it expands
Sympathy, and the imaginative range that goes with it. This Jupiter takes in more of other people's situations than most placements can, and its usefulness to them is real rather than sentimental.
It also enlarges whatever is not literal: art, faith, the parts of life that do not resolve into a plan. The tradition treats this as a fortunate placement for anyone working in those fields, which is folklore, though the affinity is consistent enough to be worth naming.
What it overdoes
Giving without assessment. Resources go to people who will not use them well, and this Jupiter continues after that has become obvious, because withholding feels worse than being taken advantage of.
It also overdoes escape. When the situation is unpleasant, the placement enlarges the exits — the drink, the fantasy, the plan to be somewhere else — and it finds them very easily.
What it is actually generous about
Forgiveness, which it hands out at a rate other placements find alarming. Someone can be re-admitted here on almost no evidence of change.
It also gives time to people nobody else is spending any on. What it does not give is a limit, and the absence of one is the reason the generosity periodically collapses under itself.
Why the dignity is what it is
Jupiter rules Pisces traditionally; modern practice assigns the sign to Neptune and keeps Jupiter as co-ruler. Both readings are in use and both are worth applying.
Under the older scheme this is Jupiter in its own sign, with nothing translating it. Mutable water dissolves rather than defines, so what expands is everything the placement declines to draw a boundary around. Rulership describes fit rather than quality: nothing here is diluted, and that includes the failures.
Against the opposite sign
Jupiter in Pisces faces Jupiter in Virgo, where the planet is in detriment. Pisces gives without measuring; Virgo measures first and gives what is actually useful, and each finds the other's method wasteful.
Read as an axis, the pair describes one problem. Pisces's development is the Virgoan discipline of assessing before providing, which this placement can adopt as a rule and then abandon the first time someone asks it for something.
Questions people ask about this
Is Jupiter in Pisces the most generous placement?
It gives with the least assessment, which is not the same thing. The tradition reads it warmly; the practical result includes being imposed on.
Why is Jupiter in rulership in Pisces?
Pisces is Jupiter's own water sign under the traditional rulerships. Dignity describes fit between planet and sign rather than quality, so the flaws are as undiluted as the strengths.
What does this placement overdo?
Giving, and escaping. Neither has a natural limit built into the sign.