Speaking of "abstract concepts", the Lines of Celestial Longitude are an abstract way of translating the the locations of celestial objects onto the Ecliptic. And, these "abstract" intersections of those Lines within the zodiacal Chart is foundational to how most of us are reading the Charts.
Celestial longitude is indeed a mean relationship, but only it can represent the real universal/cosmic placements of the planets independent of their natal placements (the twelve so-called houses). - https://www.astrologyweekly.com/forum/showpost.php?p=1022545&postcount=139