
Aristotle proposed a three-part structure for souls of plants, animals, and humans, making humans unique in having all three types of soul.
Aristotle's psychology, given in his treatise On the Soul (peri psychēs), posits three kinds of soul ("psyches"): the vegetative soul, the sensitive soul, and the rational soul. Humans have all three. The vegetative soul is concerned with growth and nourishment. The sensitive soul experiences sensations and movement. The unique part of the human, rational soul is its ability to receive forms of other things and to compare them using the nous (intellect) and logos (reason).[93]

For Aristotle, the soul is the form of a living being. Because all beings are composites of form and matter, the form of living beings is that which endows them with what is specific to living beings, e.g. the ability to initiate movement (or in the case of plants, growth and transformations, which Aristotle considers types of movement).[11] In contrast to earlier philosophers, but in accordance with the Egyptians, he placed the rational soul in the heart, rather than the brain.[94] Notable is Aristotle's division of sensation and thought, which generally differed from the concepts of previous philosophers, with the exception of Alcmaeon.[95]

In On the Soul, Aristotle famously criticizes Plato's theory of the soul and develops his own in response. The first criticism is against Plato's view of the soul in the Timaeus that the soul takes up space and is able to come into physical contact with bodies.[96] 20th-century scholarship overwhelmingly opposed Aristotle's interpretation of Plato and maintained that he had misunderstood him.[97] Today's scholars have tended to re-assess Aristotle's interpretation and been more positive about it.[98] Aristotle's other criticism is that Plato's view of reincarnation entails that it is possible for a soul and its body to be mis-matched; in principle, Aristotle alleges, any soul can go with any body, according to Plato's theory.[99] Aristotle's claim that the soul is the form of a living being eliminates that possibility and thus rules out reincarnation.[100]

Memory
According to Aristotle in On the Soul, memory is the ability to hold a perceived experience in the mind and to distinguish between the internal "appearance" and an occurrence in the past.[101] In other words, a memory is a mental picture (phantasm) that can be recovered. Aristotle believed an impression is left on a semi-fluid bodily organ that undergoes several changes in order to make a memory. A memory occurs when stimuli such as sights or sounds are so complex that the nervous system cannot receive all the impressions at once. These changes are the same as those involved in the operations of sensation, Aristotelian 'common sense', and thinking.[102][103]

Aristotle uses the term 'memory' for the actual retaining of an experience in the impression that can develop from sensation, and for the intellectual anxiety that comes with the impression because it is formed at a particular time and processing specific contents. Memory is of the past, prediction is of the future, and sensation is of the present. Retrieval of impressions cannot be performed suddenly. A transitional channel is needed and located in past experiences, both for previous experience and present experience.[104]

Because Aristotle believes people receive all kinds of sense perceptions and perceive them as impressions, people are continually weaving together new impressions of experiences. To search for these impressions, people search the memory itself.[105] Within the memory, if one experience is offered instead of a specific memory, that person will reject this experience until they find what they are looking for. Recollection occurs when one retrieved experience naturally follows another. If the chain of "images" is needed, one memory will stimulate the next. When people recall experiences, they stimulate certain previous experiences until they reach the one that is needed.[106] Recollection is thus the self-directed activity of retrieving the information stored in a memory impression.[107] Only humans can remember impressions of intellectual activity, such as numbers and words. Animals that have perception of time can retrieve memories of their past observations. Remembering involves only perception of the things remembered and of the time passed.[108]


Senses, perception, memory, dreams, action in Aristotle's psychology. Impressions are stored in the sensorium (the heart), linked by his laws of association (similarity, contrast, and contiguity).
Aristotle believed the chain of thought, which ends in recollection of certain impressions, was connected systematically in relationships such as similarity, contrast, and contiguity, described in his laws of association. Aristotle believed that past experiences are hidden within the mind. A force operates to awaken the hidden material to bring up the actual experience. According to Aristotle, association is the power innate in a mental state, which operates upon the unexpressed remains of former experiences, allowing them to rise and be recalled.[109][110]

Dreams
Further information: Dream § Other
Aristotle describes sleep in On Sleep and Wakefulness.[111] Sleep takes place as a result of overuse of the senses[112] or of digestion,[113] so it is vital to the body.[112] While a person is asleep, the critical activities, which include thinking, sensing, recalling and remembering, do not function as they do during wakefulness. Since a person cannot sense during sleep, they cannot have desire, which is the result of sensation. However, the senses are able to work during sleep,[114] albeit differently,[111] unless they are weary.[112]

Dreams do not involve actually sensing a stimulus. In dreams, sensation is still involved, but in an altered manner.[112] Aristotle explains that when a person stares at a moving stimulus such as the waves in a body of water, and then looks away, the next thing they look at appears to have a wavelike motion. When a person perceives a stimulus and the stimulus is no longer the focus of their attention, it leaves an impression.[111] When the body is awake and the senses are functioning properly, a person constantly encounters new stimuli to sense and so the impressions of previously perceived stimuli are ignored.[112] However, during sleep the impressions made throughout the day are noticed as there are no new distracting sensory experiences.[111] So, dreams result from these lasting impressions. Since impressions are all that are left and not the exact stimuli, dreams do not resemble the actual waking experience.[115] During sleep, a person is in an altered state of mind. Aristotle compares a sleeping person to a person who is overtaken by strong feelings toward a stimulus. For example, a person who has a strong infatuation with someone may begin to think they see that person everywhere because they are so overtaken by their feelings. Since a person sleeping is in a suggestible state and unable to make judgements, they become easily deceived by what appears in their dreams, like the infatuated person.[111] This leads the person to believe the dream is real, even when the dreams are absurd in nature.[111] In De Anima iii 3, Aristotle ascribes the ability to create, to store, and to recall images in the absence of perception to the faculty of imagination, phantasia.[11]

One component of Aristotle's theory of dreams disagrees with previously held beliefs. He claimed that dreams are not foretelling and not sent by a divine being. Aristotle reasoned naturalistically that instances in which dreams do resemble future events are simply coincidences.[116] Aristotle claimed that a dream is first established by the fact that the person is asleep when they experience it. If a person had an image appear for a moment after waking up or if they see something in the dark it is not considered a dream because they were awake when it occurred. Secondly, any sensory experience that is perceived while a person is asleep does not qualify as part of a dream. For example, if, while a person is sleeping, a door shuts and in their dream they hear a door is shut, this sensory experience is not part of the dream. Lastly, the images of dreams must be a result of lasting impressions of waking sensory experiences.[115]

Practical philosophy
Aristotle's practical philosophy covers areas such as ethics, politics, economics, and rhetoric.[40]
