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)
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 chemical transformations, which Aristotle considers types of movement)
In contrast to earlier philosophers, but in accordance with the Egyptians, he placed the rational soul in the heart, rather than the brain
Notable is Aristotle's division of sensation and thought, which generally differed from the concepts of previous philosophers, with the exception of Alcmaeon
In On the Soul, Aristotle famously criticizes Plato's theory of the soul and develops his own in response to Plato's
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
20th-century scholarship overwhelmingly opposed Aristotle's interpretation of Plato and maintained that he had misunderstood Plato
Today's scholars have tended to re-assess Aristotle's interpretation and have warmed up to it
Aristotle's claim that the soul is the form of a living being is meant to eliminate that possibility and thus rule out reincarnation
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
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 , and thinking
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
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
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
Recollection is thus the self-directed activity of retrieving the information stored in a memory impression
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
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
Dreams 

Aristotle describes sleep in On Sleep and Wakefulness
Sleep takes place as a result of overuse of the senses or of digestion, so it is vital to the body
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, albeit differently, unless they are weary
Dreams do not involve actually sensing a stimulus
In dreams, sensation is still involved, but in an altered manner
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
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
However, during sleep the impressions made throughout the day are noticed as there are no new distracting sensory experiences
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
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
This leads the person to believe the dream is real, even when the dreams are absurd in nature