MAHAT or MAHATTATTVA: “I” (“I am,” “I exist”) feeling, existential “I”.
AHAM or AHAḾTATTVA: Doer “I”, ego, second mental subjectivity.
CITTA: Done “I”, objective “I”, objective mind, mind-stuff.
This is the classic (earliest) categorization of the layers of the mind. This categorization applies to the Cosmic Mind as well as the individual human mind.
Even though there is “I” in the English translations of Mahat, Aham and Citta, these terms don’t really refer to the soul. My intuitive understanding is that the Mahat is not the soul. Mahat is the subtlest layer of mind around the soul which is the life giving core of our being. Mahat refers to the subtlest layers of the mind, and Citta refers to the densest layers of the mind.
At a later stage another categorization emerged among the spiritual philosophers. In this categorization there are 7 realms in the Cosmic Mind and 5 layers of the human mind.
Satyaloka: The realm beyond Cosmos. The realm of the Cosmic Soul (Parama Purusha)
Tapahloka: The spiritual realm of the Cosmos. Tapah Loka is the first layer around the Cosmic Soul. Tapah Loka is the realm of Divine Love.
Janahloka: The realm of true knowledge and wisdom.
Maharloka: The realm of ideas and abstractions.
Svarloka: The realm of feelings and memory.
Bhuvarloka: The primordial fabric (Cosmic Citta). The stage before the physical manifestation. This is also the realm of vital currents and microvita.
Bhurloka: Physical universes are embedded in this realm.
Kamamaya Kosha: The material body including the brain and the nervous system is controlled by the Kamamaya Kosha which is also known as the “subtle body.” The vital airs (flows of vital energy) in our subtle body are part of the Kamamaya Kosha. The Ancient Egpytians referred to the Kamamaya Kosha as Ka. In the Western literature Kamamaya Kosha is known as the “etheric body.” Kamamaya Kosha is derived from Bhuvarloka.
Manomaya Kosha: The Manomaya layer of the human mind contains the mental structures: ego, intellect, memory as well as emotions and feelings. The dreams during sleep take place in the Manomaya Kosha as well. Manomaya Kosha is the psyche. The waking consciousness, dreaming consciousness and the “subconscious” of the Freudian psychology belong to this layer. The “thinking mind” is in this layer as well. Manomaya Kosha is derived from Svarloka.
Atimanas Kosha: The contemplative faculty of the human mind. Atimanas Kosha is derived from Maharloka.
Vigyananamaya Kosha: The intuitional faculty of the human mind.
Hiranmaya Kosha: The seat of the soul. Humans experience Divine Love and true happiness in the Hiranmaya Kosha. In some spiritual traditions the Hiranmaya Kosha is known as the Heart.
More recent categorization
Baba (Shrii Shrii Anandamurti) introduced the “Knower I” and “Known I” concepts in 1989, a year before his death in 1990. He introduced these terms in the context of the Microvita Theory. He mentioned that this is a new way of thinking in spiritual philosophy.
I did a careful reading of his discourses again. It seems to me that in the new paradigm Baba wanted the soul to be mentioned explicitly in the terminology.
Here’s my understanding of the new categorization:
Knower I : Soul + Mahat
Doer I : Soul + Aham
Done I : Soul + Citta
Known I : Soul + Matter
The soul has to be mentioned explicitly in the terminology of spiritual philosophy because there is no manifestation and there is no life without the soul.
Remember that the Sanskrit word for soul is purusha.