Houses and aspects

What it is

Two structural elements without which a chart is just a list of planetary positions.

Houses divide the local sky as seen from the birthplace, keyed to the horizon at that moment. Where the signs say how a planet expresses itself, the houses say where in life — the first house concerning the self and body, the seventh partnership and open enemies, the tenth career and public standing, and so on. Houses depend on the exact time and latitude, which is why birth time matters so much.

Aspects are the angular relationships between planets, measured along the ecliptic. The classical five are conjunction (0°), sextile (60°), square (90°), trine (120°) and opposition (180°). Squares and oppositions traditionally indicate friction; trines and sextiles ease. An aspect is considered active within an orb — a tolerance of some degrees either side of exact.

Where it came from

Houses appear in the earliest Hellenistic material, originally as whole sign houses: the sign containing the ascendant is the first house, the next sign the second, and so on. Simple, and requiring no calculation beyond the ascendant.

Quadrant systems, which divide the space between the four angles rather than by sign, developed later and multiplied. By the medieval period there were several; by the modern period more than a dozen. Placidus, devised in the seventeenth century, became dominant largely because its tables were the ones widely printed and sold in the nineteenth and twentieth centuries.

The aspects are Ptolemaic in their classical form and were justified geometrically — the divisions of the circle by two, three, four and six. Kepler extended the set on harmonic grounds, as described in his article, and modern astrologers have added further minor aspects.

How it is used

The astrologer notes which house each planet occupies, which sign is on each house cusp, and which planets rule those signs — then reads the aspect network to see which parts of the chart are connected and how.

What we can and cannot say

We can say the machinery is sophisticated and the internal logic is real. This is not arbitrary; each element has a rationale within the system.

And we can say that this is where astrology's most serious problem lives, and it is not the problem sceptics usually raise. The external evidence question is covered elsewhere. The internal question is sharper:

Practitioners cannot agree on which house system is correct, the systems give different answers, and there is no procedure for settling it.

This is not a small discrepancy. A planet near a cusp can fall in the ninth house under Placidus and the tenth under whole sign — career rather than travel and higher learning, a materially different reading. Every practising astrologer knows this. The usual response is that a practitioner should use whichever system works for them, which is an answer no discipline with an external check could give.

The problem gets worse at high latitude. Time-based systems including Placidus break down near the poles: as the ascendant's motion becomes extreme, houses distort grotesquely and above the Arctic and Antarctic circles some cusps become undefined. Software handles this by substituting another system or refusing. A model of celestial influence that cannot produce an answer for someone born in northern Norway has a structural fault, not a rounding error.

Orbs have the same character. How wide is an aspect's influence? Answers range from a few degrees to ten or more, vary by planet and by astrologer, and are set by convention and taste. A parameter that each practitioner chooses for themselves, which determines whether a given feature exists in a given chart, is not a measurement.

We can say why this persists: there is no outcome to check against. In any field with an external standard, competing methods get tested and the losers are dropped. Astrology has no such standard, so incompatible systems coexist indefinitely, each with sincere practitioners reporting that theirs works.

We cannot say which system is right, and neither can the tradition — which is the point. The disagreement described in tropical and sidereal is the same shape at a larger scale. A discipline can be internally rigorous, historically deep, technically demanding, and still have no mechanism for discovering that any part of it is wrong.

Further reading

• Ralph Holden, The Elements of House Division (1977) — a working astrologer's survey of the systems and their rationales.
• Any chart-calculation program with a house-system dropdown — switch it and watch the reading change.