The astrological chart is a circle that can be divided in various ways. One is into twelve parts corresponding to twelve signs of the zodiac. This creates twelve houses. In a flat or equal house chart, all the houses have 30 degrees equally. In a chart employing Placidus, Koch, or Campanus calculations to cast the Wheel, the houses will be unequal divisions of the 360 degrees of a circle though each sign will never exceed its 30 degrees. With unequal house systems, a sign rarely begins at a cusp (line) and rarely completes at the next cusp. If you have your birth chart, your Ascendant or the MC (medium coli) are good examples of this. My ASC (rising sign) is 17.08 Sagittarius. This indicates that Sagittarius began in my 12th house and that 16 degrees plus 22 minutes of Sagittarius are in the 12th house.

A second division of the circle is in halves horizontally or vertically. The former creates the horizon line and notates the sign that was on the horizon at the time and location of birth or beginning of what the chart is for (a business or marriage or endeavor). The rising sign (ASC/ascendant) sets the 1st house cusp; it is the beginning of the Wheel. The opposite point on the horizon is the Descendant and the 7th house cusp. A vertical line produces the MC/10th house cusp and the IC or nadir/4th house cusp. The meaning of all four points is, however, derived from the horizon and the horizontal which objectifies the day and night of the chart: day is above the horizon, night is below. I have mentioned in previous articles that planets in the10th and 9th houses are visible, their characteristics in the native display prominently like the sun does in the peak of day. The 4th house is like a womb or burrow or hollow of a tree. It is where we emerge from which is foundational to our life expression. It is also where we return to at the end of the day. More of this when the 4th house is taken up in this series.
The vertical division gives East and West of a chart because the sun rises in the East and sets in the West. The rising sun provides that life can begin its daily course. The sense of personal volition and autonomy or personal initiative go with the East of a chart. The West of a chart gives the feeling of dependence upon causes and conditions, circumstances and people in order for momentum to get going. Even if one tries to initiate something, it likely won’t take hold. Others are needed. This all comes from the energetic that the sun is setting through the 8th and 7th houses and then is moving into the night of the chart after that. Metaphorically, one can’t see and needs the help of others to accomplish a goal or task.
This explanation is to set up the 6th through 1st houses and their articles. It is traditionally said that those houses have an inner, or internal, or subjective quality to them. This is due to the night of the chart that they represent.