Having been asked which houses refer to knowledge and truth…:
…In my understanding the 12th is the home of Pure Truth, Oneness, All-Potentiality, the Principle of the Gestalt of Time that will become life in the course of the emanation towards physical-material appearance (expressible also as phases of the zodiac). Only the Absolute is completely Pure. Human life is not, and is not meant to be ;)))
(Of course in practice the 12th is also home of the negation and repression of the Godly/Absolute, of the Principle, all the seeds that never sprang into existence and life and now still wait to emerge from the 12th, sadly however mostly as the negative expression of their having been excluded…)
In general I see four houses/signs connected to knowledge:
The 3rd: LOGIC: linear logic, knowledge of facts, knowledge dealing with the physical-material world;
The 6th: REASON: Sense perception of the circumstances and conditions of life. This leads to awareness and consequently to analysis, articulation and comprehension of these conditions. It is a protective function of the subjective being, adapting it to the world beyond itself, to THE OTHER that is encountered in the 3rd quadrant.
So, the overall meaning of „reason“ is the protection of the subjective being, ensuring survival by adapting it to the world beyond itself and by protecting it also against the danger of its own boundless subjectivity. Sense perception, awareness, analysis and comprehension are the way to ensure this.
The 9th: UNDERSTANDING: Understanding of the world, already having encountered the Other. Understanding as a landscape of concepts (philosophy, religions, taking in other cultures…). The 9th is beyond subjective needs. It does not serve the survival of the subjective like „reason“ of the 6th does, but it is a function of consciousness, in that it includes and introduces the objective world to the individual’s consciousness.
The 9th CAN contain truth, when the encounters with the outside world, which take place in the 7th and are structurally organised in the 8th, have finally been arranged to a truthful and genuine philosophy in the 9th, alive, not hardened to ideology.
It CAN contain truth, if – in the other direction – the experience of truth in the 11th house reflects in the 9th house’s understanding of the world. But usually all human beings are subject to biases, and accordingly the 9th is already tainted by these biases. The 9th is religious BELIEF in contrast to religious EXPERIENCE (in the 4th quadrant, specifically in the 11th).
The 12th: ABSOLUTE KNOWLEDGE, CERTITUDE; a knowledge that results from identity with truth in the 12th. It cannot be questioned, nor proved or justified rationally. It is simply a connection to heavenly truth, even if only for a moment in time. There is of course always a danger of mistaking something else for it ;) – especially ideological persons tend to mistake mania for absolute truth. Only heaven knows for sure, and time will tell… True knowledge usually has no motive to be shown and to be „delivered to the world“ by a messiahs