That is to say, he explained the two laws; Law of Suiko (although the sky is originally flat, from the eyes of an observer, it looks as though it hung down in four directions with the space above the observer as the center, and it also looks like a semicircle); and the Law of Shukusho (the observer has an illusion that the area near his/her head looks spacious and the area near the ground looks narrow).
すなわちそれが垂孤の法則（天は本来平面であるが、見た目には観察者の頭上を中心に東西南北に垂れ下がり、あたかも半円のように見える）と縮象の法則（頭上に近いあたりは広く、地面に近いあたりは狭く見える錯覚を起こす）という主張である。