Quick answer: The Lot of Basis (Greek Klēros Baseōs, "foundation") is a calculated point in Hellenistic astrology built not from planets but from two other lots, Fortune and Spirit. It marks the support and physical stability of a life, read descriptively by sign, whole-sign house, and ruler, never as an event forecast.
Among the many lots of Hellenistic astrology, Basis is unusual: it is built from two other lots rather than from an arc between two planets. Understanding it means first understanding the two great lots it rests upon.
What Is the Lot of Basis? The "Foundation" Point
The name comes from the Greek basis (βάσις), meaning "base, step, or pedestal," the support on which a structure stands. In the natal chart the Lot of Basis, also called the Lot of Foundation, signifies exactly that: the underpinning and physical stability of the life, the common ground on which the whole nativity rests. The later compiler Rhetorius describes it as an accessory cause of life and breath, pointing to bodily matters and physical security. Vettius Valens groups it with Fortune, Spirit, and the Lot of Exaltation when weighing a native's standing. It is a supporting significator, not a headline oracle.
Built From Two Lots: Fortune and Spirit
Basis rests on the two great lots of the tradition. The Lot of Fortune is the lunar lot of body, health, and material circumstance; the Lot of Spirit, also called Daimon, is the solar lot of mind, will, and action. Both are found by projecting the arc between the Sun and Moon from the Ascendant, and both reverse by sect. By day, Fortune is Ascendant + Moon - Sun and Spirit is Ascendant + Sun - Moon; by night the two formulas swap. Because they are mirror images across the Ascendant degree, Fortune and Spirit always sit equidistant from the Ascendant in opposite directions. That symmetry is what makes Basis possible.
How to Calculate the Lot of Basis
Take the shorter arc between Fortune and Spirit, the separation of 180 degrees or less, and add it to the degree of the Ascendant in zodiacal order. Add the arc whole, not halved. The classical sect statements, measuring from Fortune to Spirit by day and from Spirit to Fortune by night, converge on the same degree, because the shorter arc is direction-independent. A useful self-check follows: since the added arc is never more than 180 degrees, Basis always falls in the lower hemisphere, in whole-sign houses one through six counted from the Ascendant. If your result lands above the horizon, the calculation is wrong.
| Lot | Day formula | Night formula | Luminary in formula | Core signification | |---|---|---|---|---| | Fortune | Asc + Moon - Sun | Asc + Sun - Moon | Moon | Body, health, material fortune | | Spirit | Asc + Sun - Moon | Asc + Moon - Sun | Sun | Mind, will, action, career | | Basis | Asc + shorter arc (Fortune to Spirit) | Asc + shorter arc (Spirit to Fortune), same degree | none | Foundation, physical stability, support |
Footnote: the Lot of Basis always lands in whole-sign houses one to six, below the horizon. If yours does not, recheck the arithmetic.
What Basis Signifies, and How to Read It
Read as the foundation of the chart, Basis describes how firmly and where a life is anchored. It tends to characterize the constitution and the physical support underlying both the Fortune factor of body and circumstance and the Spirit factor of mind and action. Like every Hellenistic lot, it is judged by three things: its zodiac sign, its whole-sign house, and the condition of its domicile ruler. A lot in a fixed sign whose ruler is well placed and dignified is associated with steadier footing; a ruler set in a difficult house tends to describe a foundation that is tested. Judge it by sign and ruler rather than by degree-based aspects or orbs, since the classical lots are read through whole-sign relationships. To weigh a ruler's strength you will want a working grasp of planetary dignities.
A Descriptive, Not Predictive, Point
Even in the surviving classical corpus, Basis is used sparingly and alongside Fortune, Spirit, and the Ascendant, never as a stand-alone forecast. It maps structure, not outcome. The psychological readings you may meet, "the foundation of the self" or "inner groundedness," and its revival as a headline chart factor are (modern) framings from the contemporary traditional-revival community, useful as metaphor but distinct from the classical usage. Basis is also not one of the seven Hermetic Lots, which are Fortune, Spirit, Eros, Necessity, Courage, Victory, and Nemesis; it is a separate point derived from two of them. Its value lies in describing the underlying stability of the whole nativity, in conditional and characterizing language, rather than in predicting events or their timing.
Frequently Asked Questions
Is the Lot of Basis one of the seven Hermetic Lots?
No. The seven Hermetic Lots are Fortune, Spirit, Eros, Necessity, Courage, Victory, and Nemesis. Basis is a distinct point derived from two of them, Fortune and Spirit, and functions as a supporting significator rather than one of the core seven.
Do I halve the arc between Fortune and Spirit?
No. Add the shorter arc whole to the Ascendant, counting forward in zodiacal order. Halving is a common error. Because the arc is 180 degrees or less, the finished lot always lands below the horizon, in whole-sign houses one through six.
Does the day or night formula change the result?
The sect statements describe the measurement from opposite ends, Fortune to Spirit by day and Spirit to Fortune by night, but because you always use the shorter arc, which is direction-independent, both converge on the same degree. Sect matters for calculating Fortune and Spirit themselves, not for the final Basis degree.
Can the Lot of Basis predict specific events?
No. Read it descriptively, as an indicator of constitution, support, and stability by sign, whole-sign house, and ruler condition. It describes the foundation of the life, not a timeline of outcomes.
Find Your Lot of Basis
To locate your Lot of Basis you first need your Ascendant and your Lots of Fortune and Spirit, all of which you can generate with our free birth chart tool. For a fuller reading of how these foundations shape character, our personality report works through the chart in context, and you can explore more classical techniques on the blog.
