Throughout history, in different times and in different areas of thought, mind was very differently conceived than we do today. Here is shown an unconventional design to modern science, which is the idea of soul as something material, in one hand, yet not totally contained within the physical limits of the body or located in any specific part of the body, in the other.
This idea, that can be shocking, is that of an 'extensive' soul, a material element that acts on the body. This soul would be 'made' of a non-solid, much more subtle than the body, almost imperceptible, like air or breath, but also physical.
Initially it is difficult to understand a conception like this, in which the most human, what defines us as persons, ceases to be located within 'us' in the misunderstanding that 'we' are simply 'our body'. In our interpretation the soul as an exclusive product of nervous system function disappeares, it does not 'emerge' spectacularly from brain activity. This contradicts apparently some fundamental assumptions to modern science. But, not being this soul anything metaphysical or immaterial but just pure matter, also seems to contradict the religious dogmas.
One idea of the soul and mind like this encounters with religion (see the case of Michael Servetus for example) and initially gives the impression that escapes the 'scientific' study or, at least, is strange to the philosophical and psychological 'scientific' paradigms, but, ultimately, persists in many manifestations of popular tradition and in imagination and beliefs of people. The existence of an ethereal soul that 'comes' from nature and that 'moves' the body, that literally gives life to it and its ability to move and act, and that is the ultimate cause of acts of the subject, is an idea that, even today, illuminates thinking of many people and appears repeatedly in many expressions of oral and written tradition worldwide.
This appears over entire literary tradition of ancient mythology, in the orphism, in Homer, in the Ionian philosophers thinking, in fairy tales and fantastic stories, it appears in Hippocratic Corpus, in Ibn Arabi and Michael Servetus writtings, in Maister Eckhart, in Shakespeare... And generally is given a deep meaning to it extremely intimate and poetic related to the sense of life and the individual's link with nature and the universe. This is a no ordinary topic but, on the contrary, is quite poetic. The words of Emerson and Hölderlin perfectly could illustrate this sensitivity we speak about.
In Homer the soul is regarded as strictly material: a spirit or a ghost, something vaporous surrounding the body. Homer speaks in particular of 'zimos', the 'substance of life', the steamy breath of the soul, the active material, the sensing and thinking one related to air-spirit and to blood. It is a physical substance, but vaporous, not solid, and not just an inert material but active. In fact it is what provides activity to human body when is in contact with it. Provides the ability to feel and think, carries life and activity, moves and encourages the body... It is the principle of life. It leaves us, Homer says, when we vanish or, with our last breath, when we die. The human body is totally inert without it. The zimos only manifests itself when acts on the blood that runs through the living body, when, as air, gives breath to the body and so life and the ability to think. Air, blood, life and thought are inseparable.
However, when this type of stuff does not touch nor act on a body, but exists, has not the ability to manifest in a vital and mental way. Homer called 'psyche' to this condition, and reduced it to that which remains, with no real consciousness, in the 'house of Hades', while it has not a living body and does not feed on blood. Somehow the psyche exists only potentially, it consists of unrealized ideas that can manifest but they do not, of potential content of thought but not real mental activity. They are only ideas not expressed in any vital (mental) act.
To Homer the conscious life and thought processes are not confined to the ideas themselves, in abstract, but they go beyond and depend, more than of ideas as informational content, of the action of air on blood throught breathing, namely of the psychobiological act that makes the ideas 'live': the zimos.
The soul is identified with the engine of the living body and is considered the principle of life. It spreads throughout the body, through breath and blood, from lungs and the heart. Clearly, this Homeric soul corresponds to the air introduced into the body by the action of lungs (breath), which spreads around it through blood and the heart and finally manifests in the mental activity as the form of vital activity that it is.
Another term used by Homer to refer to mind was 'frenes'. This term originally meant, in this author, 'lungs and heart', precisely. With frenes Homer did not refer directly to air or breath of the soul, which corresponds to zimos, but to body organs through which the air or breath acts and manifests on soul and mind.
Homer shows repeatedly in his work a mind-body dualism that persist in later Greek authors. This dualism, says Popper, is typical of the ancient tendency to think in terms of mortal-immortal polar antithesis. The body is mortal and the soul is immortal. In Homer the soul, but immortal, is just a material element, although different and irreducible to the stuff of the body. In fact (and this is important) this is a materialistic dualism. The soul is identified with life, with material elements of life like breath and air, and blood, and involves the functioning of body organs. But it is not confined to them; physically transcends the body, comes from outside and is immortal, as the air is.
In the Ionian philosophical tradition, the so-called physical philosophers, from Anaximenes to Diogenes of Apollonia, the Homeric conception of the soul remains almost intact: the soul is essentially air. We know this, in part, by Aristotle, who also said about the ancient religion of Orpheus "called Orphic poems say that the soul, carried by the winds, fully fits animals when they breathe". Aristotle himself located in the heart, the organ that distributes the air with the blood throughout the body, the seat of consciousness.
As Guthrie points out, to Aristotle 'psyche' meant "not only a soul, but soul in general, namely a kind of psychic material that filled the world”. Indeed, it seems that Aristotle himself, as the preceding materialist thinkers, considered the soul as air, and the particular soul as an air parcel, because the soul must be the lighter form of matter that people knew, which was the air.
Before Aristotle, Anaxagoras stated that “the mind is the most rarefied and purer stuff; it knows everything about anything and has the ultimate power. Moreover, anything that has life or 'psyche', the largest body and the smallest, it is governed by the mind yet”. To Anaxagoras, the mind is the principle of movement and order and, consequently, it is the principle of life. And he distinguishes the mind from all other substances as the more 'rarefied and pure', namely something ethereal or 'air'. And he identifies this 'ethereal stuff' as the cause of knowledge that governs mind and life of organisms, like the zimos of Homer.
To Heraclitus, the soul is fire. Not so much a substance as a process. All material stuff flow, all are processes, the universe as a whole included. Each is governed by the order or 'logos', an universal intelligence. To Heraclitus, fire is the most powerful material process, purer and also the finest and subtle. And so he identified it with the soul. Fire is the 'logos' and is the soul, which subsumes both the man and the entire universe. The soul is not the air itself yet, but the fire, the process in which air is consumed. Soul is not a state of the air but a process (of consumption) of it.
To Democritus, probably the most consistent materialist thinker, the soul is composed of smaller atoms. They are especially suitable for round and move through all things and to move one to others through their own movement. According to Aristotle they are the same atoms of fire. This little soul atoms penetrate the body and distribute so that they alternate with bigger bodily atoms and act on them through their inner movement.
In addition, Democritus concretes that "the soul has two parts: one that is rational, located in the heart, while the irrational is dispersed throughout the entire body". Briefly, the soul acts on the body in a totally mechanical force exerted by atoms on the full extent of the body, force that has its origin in a rational order generated in the heart. This is more or less the same: small atoms, round, dynamic, similar or identical to those of fire (which is the process of consumption of air, remember) that are distributed throughout the body and provides order and 'reason' (mind) from the heart (blood circulation again).
The Hippocratic School held a similar approach on the soul, despite putting in the brain the seat of feeling, thought and movement control, instead of the heart. They explain that the air is what gives intelligence to the brain (throught blood) and interpret very explicitly this air as the highest soul. The air contributes directly to intelligence. The location in the brain is argued in the sense that when a man introduces air into himself (by breathing), this air always reaches the brain at first (from blood circulation), they say, and thus acts on it with all the power of a 'logos-order-intelligence' inherent to the intact and pure air, which many people consider 'divine'.