Plato (c. 427-347 B.C.E): Intellect (Nous) is the highest part of the human soul. Through it man can gain wisdom, which consists in contemplating the immutable, eternal, incorporeal ideas.
(need world of forms to account for intellect)
Aristotle: (384-322 B.C.E.) 
Soul is to body as matter is to form. The soul is the first actualization of the body, its capacity to exercise the functions that make it a living thing. He distinguishes several different faculties of the soul. – different ways in which something can be alive: nutrition, reproduction, sensation, desire, movement, imagination and intellect. Not all living things have every faculty. The human soul has two cognitive faculties: sensation and imagination (imagination once object sensed is no longer present). The intellect must be receptive to the forms of things in the same way as the faculty of sensation. The intellect is in potency to become the same as its object: until it thinks, it has no existence in act; its only characteristic is its capacity to receive. Aristotle distinguishes the workings of the intellect from those of the sensitive faculty in two ways. The sensitive faculty has organs, whereas the intellect has none. And the object of intellectual knowledge differs from that of sensible knowledge: the intellect perceives the essences of things: not the straight line but straightness, not flesh but what it is to be flesh… When the intellect thinks these essences, its thought is undivided and there can be no falsehood. Thought can’t take place without sensible images (phantasmata). Words do not stand directly for things in the world, but for ‘affections of the soul’. These affections are the same for all men, despite the different spoken and written languages they use.
Active intellect actualizes potential of passive intellect, which exists only potentially until it is informed. Potential Intellect characterized as “becoming all things” and Active Intellect “is so by producing all things, as a kind of disposition, like light does; for in a way light too makes colours which are potential into actual colors. And this intellect is distinct, unaffected, and unmixed, being in essence activity.” [This treatment] can be taken depending on the interpretation either as affirming or denying that there is an immortal part.
(Accounts of intellect involve connecting faculties to objects.)
Lloyd P. Gerson: “The perennial problem in interpreting De Anima 3.5 has produced two drastic solutions, one ancient and one contemporary. According to the first, Aristotle in 3.5 identi fies the 'agent intellect' with the divine intellect… In contrast to this ancient interpretation, a more recent view holds that the divine intellect is not the subject of 3.5 and that throughout the work Aristotle is analyzing the nature of the human intellect. But this view contends that the properties Aristotle deduces for this intellect, properties that have encouraged the view that Aristotle must be speaking about a divine intellect, are in fact to be discounted or interpreted in such a way that they do not indicate the immortality and immateriality of the human intellect. In this article I argue that close attention to the text and the sequence of argument supports the conclusion that Aristotle is speaking throughout De Anima of a unified human intellect, possessed of the properties Aristotle explicitly attributes to it. This intellect functions differently when it is and when it is not separate from the hylomorphic composite. I argue further that it is Aristotle's view that if we were not ideally or essentially intellects, we could not engage in the diverse cognitive activities of this composite.”
Alexander of Aphrodisias (early 3rd century C.E.): “Like Aristotle, but unlike almost all his expositors, Alexander did not assign a role to the active intellect in the process of human cognition. The material intellect, he thought, itself has the power to abstract universals from sensible particulars. As a person exercises this powerand is instructed by others, he develops a disposition to engage in intellectual thought—for his intellect to be in act.” Active intellect is the Divine Intellect, “described as an ultimate source of the intelligibility of things, probably because it has made them such that they can be thought by the intellect.”
Themistius (317 - ca. 387) believes that it is clear from Aristotle’s account that each individual soul has an active as well as a potential intellect. Yet he believes that there must be a single active intellect in order to account for the common intellectual conceptions which everybody shares. He therefore suggests that there is one first active intellect which illuminates the active intellect in each human soul. The illuminated individual active intellect illuminates both the potential intellect and the sensible forms, which are intelligible in potency; by doing so, it brings about intellectual knowledge. Themistius says little about what the first active intellect is, except to make it clear that it cannot be identified with God.
[1st or 2nd century] Middle Platonic anonymous Parmenides commentary and Chaldean Oracles, Gnostics
examples of pre-Plotinian mysticisms based on assumption of hypercosmic One, not yet “Union” with…
Plotinus: (204-270 C.E.) union of active and passive during moment of conjunction (in ordinary cognition) becomes model for supra-rational (ineffable) union with hypercosmic one (resonances with En Sof)
Iamblichus ca. 245 - ca. 325): “thought alone” not sufficient for ascent/union. The mystic must learn the correct performance of theurgic rites, which work by means of sumbola/sunthemata: ineffable symbols placed in material things by the gods. Iamblichus’ strong concern is to distinguish theurgy from magic, which according to the Plotinian model works according to cosmic sympathy, and has no operative power in the hypercosmic realms that the theurgist deals with. Once the soul is purified by the “material rites” which address the problems of the lower parts of the soul (the “garments” which must be stripped away) the soul becomes in some sense “deified,” although Iamblichus is concerned to mitigate Plotinian fluidity of subject and object. The theurgist rises above fate to become installed into the divine system of “intellections of the demiurge” but retains his own identity (which in the Plotinian model collapses in the blurring/unification of subject and object). Iamblichus also takes issue with Plotinus’ doctrine of the “undescended soul” which holds that there is a spark of the highest intellect within the soul. Iamblichus’ greatest successor Proclus will develop this “late neoplatonic iamblichean turn” into a model of turning to the likeness of the “one within us,” which is the most spiritual form of sumbola/sunthemata:
[?-500 C.E. “or so”] Enoch literature… Hekalot texts… Sefer Yetsirah
10th century Sefer Yetsirah emerges, used in cosmological speculation
Avicenna (980-1037): origin of intellectual knowledge must be beyond powers of individual soul
Subject of De Anima the soul in conjunction with the body, soul held to be separable.
Unlike Aristotle he doesn’t hold that the soul is merely the capacity for the functions of life of a suitable natural body… the soul uses the body as an instrument… Rejects Arist. idea that that the intellect is converted from potential to act by becoming what it thinks. It is the Agent Intellect which makes the human intellect know in act, by providing it with intelligible forms… Intellectual ideas –unlike sensible forms—can’t be stored. Learning is not a matter of putting information away, but of acquiring the ability to join the intellect with the Agent Intellect… The embodied soul does not generally have the power to receive forms from the Agent Intellect without preparation; learning brings the capacity to do so. Treatment of the inner senses… account aims to be physiological. Avicenna is here dealing with working of the soul which require corporeal instruments, and each of the internal senses is situated in a part of the brain. 
Averroes (1126-1198) argues that the potential (or, as he calls it, material) intellect is one for all men.
Knowledge-in-us differentiated by forms or “intentiones” in the imagination… The forms in the imagination are only in potency to move the material intellect; the Agent Intellect makes them able to do so in act… both intellects are ungenerated and incorruptible. The material intellect, when brought into act through the intervention of the active intellect, can be called the ‘speculative’ or the ‘made’ intellect. As that which receives, the speculative intellect in the material intellect and so is unique and eternal; but with regard to the intensiones it receives it is many, generated, and corruptible. Agent Intellect “primarily continues with us only in contact with the material intellect” (…worries about immortality/conjunction)
Ibn Gabirol (1021-1058)
All created things are different from God and understood to be differentiated in their being composed of form and matter. God alone is not composed of form and matter—this is called “universal hylomorphism” and must not be confused with pantheism (also need not be described as “panentheism” or “emanationism”). Emanation is of divine energies and rays not essence. The divine Will is the transcendent force that is understood as composing form and matter at every ontological level (except for the divine). The action of the mind is seen as the complement to this divine “downward motion,” along Aristotelian lines the mind abstracts intelligible form from sensible matter; once this is accomplished (“resolved”) one will find oneself at the next ontological level. Beyond the first hypostasis of form and matter, the level of Intellect, lies union with the divine Will. According to Gabirol what follows is not union with the essence of the one, but a “circling about” the essence. His account doesn’t employ Jewish imagery (esoteric or otherwise). The focus on the divine Will is distinctive to Gabirol’s reading of neoplatonism.
Maimonides: prophecy as an overflow of the Agent Intellect
Abulafia: Sefirot as ten separate intellects, Agent Intellect is Angel Metatron
R. Isaac of Acre: (late 13th/early 14th c.) “he cast off all sensibilia and he desired only the Divine Intellect”
R. Nathan (a student of Abulafia? quoted in R. Isaac’s Sefer Me’irat ‘Einayim): “when man leaves the vain things of this world, and constantly attaches his thought and his soul above, his soul is called by the name of that supernal level which it attained, and to which it attached itself. How is this so? If the soul of the practitioner of hitbodedut was able to apprehend and to commune with the Passive Intellect; likewise, when it ascends further and apprehends the Acquired Intellect, it becomes the Acquired Intellect; and if it merited to apprehend to the level of the Active Intellect, it tself is the Active Intellect; but if it succeeds in clinging to the Divine Intellect, then happy is its lot, for it has returned to its foundation and its source, and it is literally called the Divine Intellect, and that man shall be called a ‘man of God,’ that is, a divine man, creating worlds because behold “Rabba created a man”… purpose of hitbodedut “to remove the thought process from objects of sensation, and to lift it up to the intelligibles or even to the highest levels of the world of Intellect… the attainment of union with the divine intellect is, however, not the ultimate attainment of the former idle man.” R. Isaac: “When man separates himself from the objects of sensation and concentrates and removes all the powers of his intellective soul from them, but gives them a powerful elevation in order to perceive Divinity, his thoughts shall draw down the abundance from above and it shall come to reside in his soul. And that which is written, “Once in each month” is to hint to the practitioner of hitbodedut that his withdrawl from all objects of sensation must not be absolute, but rather “half to God and half to yourselves,” which is also the secret of the half-shekel, “the rich man should not add, nor the poor man subtract, from the half-shekel,” whose esoteric meaning is “half of one’s soul,” for shekel alludes to the soul.” (gematria: numerical equivalent of sheqel like nefesh is 430, division refs to sensory/intellectual)
 much of this is digest/summary/paraphrase of John Marenbon, Later Medieval Philosophy 95-102
 Averroes will elaborate this into a hierarchy of faculties graded by more or less abstract (spiritual) objects
 De Anima 3.5
 "The Unity of Intellect in Aristotle's De Anima" Phronesis: A journal for Ancient Philosophy, Volume 49, Number 4, 2004, pp. 348-373(26)
 see for example Mind and Imagination in Aristotle by my former professor Michael Wedin
 John Marenbon Later Medieval Philosophy 102
 John Marenbon Later Medieval Philosophy 103
 see John Finamore Iamblichus on the Theory of the Vehicle of the Soul
 see Joseph Dan, Jewish Mysticism: Late Antiquity (1998) p.155
 John Marenbon Later Medieval Philosophy 103-105
 John Marenbon Later Medieval Philosophy 106-108
 (paraphrased from a conversation with PhD student Jason Van Boom, who did his GTU MA on Gabirol)
 Elliot Wolfson Abraham Abulafia, Kabbalist and Prophet 94-177