So far, in relation to part 2 of the Ethics, we have only spoken about the mind and not the body (and the mind in relation to the attribute of thought). The particular nature of human beings, however, is that they are the union of a mind and a body. What, then, is the relation between the mind and the body? First of, unlike Descartes, Spinoza begins with the body not the mind. If we are going to understand the nature of the human mind, we first of all have to understand the nature of the human body. This quite is different from Descartes who believes that the union of the body and the mind must be thought from the vantage point of the mind and not the body, and the mind is the truth of the body and not the other way around.
When we are thinking about Spinoza’s parallelism we are thinking about the relation between human thought and the attribute thought. For Spinoza the true ideas of thought are independent from us. These are necessary truths belonging to the causality of thought and not to whom or what thinks them. When we are thinking, however, about the nature of human thought itself, and not just its relation to the attribute thought, then we have to think of the relation between our bodies and our minds, because this is the kind of beings that we are. We already saw from last week’s lecture that the idea for Spinoza has two sides: one side is the idea itself, which Spinoza calls its formal reality, and the other side, is the object that it represents, which Spinoza, following general practice, calls its objective reality. No idea can be defined without these two sides. When we thinking about the nature of thought itself, and not just the human mind, then we are thinking just about the formal reality of ideas, the necessary causality of thought. When we are thinking about just the human mind, though, we focus on the objective reality of ideas. We have to ask ourselves ‘What is it that the human mind represents?’ Spinoza answer to this question is that the human mind represents the human body. We have to be very clear about what this answer means. It means that body is the essence, definition, or content of the mind. What the mind represents is the body, and not itself. Without the body, the mind would be nothing at all; it would have no objective reality. Thus in the scholium to P13, Spinoza will say that the complexity of the human mind, as opposed, for example to the mind of a dolphin, is to do with the complexity of the human body, and not with human mind. It is because our bodies can feel, experience, sense more that our minds are more complex than other animals, and not the other way around. We do not have complex bodies because we have complex minds, but we have complex minds because we have complex bodies. As Spinoza writes in the scholium to P13,
In proportion as a body is more capable than others of doing many things at once, or being acted upon on in many ways at once, so its mind is more capable than others of perceiving many things at once.
This explains why the next section of Part 2 has to do with the general nature of bodies. If we are to understand the human mind through the human body, then we have to understand the nature of the human body first. The human body, of course, is acted upon as any other body is in nature. To put it within a modern context, to understand human psychology we first of all have to understand physics and biology. For Spinoza’s interests in the Ethics is human happiness, then the central idea in this excursus, as Curley indicates, is the idea of the composite body, which is a body that can be acted upon by many external bodies without losing its identity (Curley 1988, p.76).
There are many different bodies in nature: basic chemical elements, simple material objects, simple organisms, and more and more complex forms of life. For Spinoza, the human being is a very complex living organism that is made up of many individual bodies, and is affected by many other bodies, in very many complex ways. What we can or are able to know for Spinoza, is directly related to the complexity of our body to be affected: everything that we know, from the simplest and most basic, to the most complex and extraordinary, first has to come to through the experience of our bodies.
The relation of the mind to the body also explains the limitations of the human knowledge, and the possibility of inadequate ideas. If we have inadequate ideas, then it is because we have a confused or distorted understanding of the body. Thus a false idea, or an inadequate idea, is not false at the level of the mode of thought or mode of extension, but in the relation between them. To understand this relation we have to understand how the human mind comes to inadequate ideas of things.
For human beings, our perception of things, which is the first level of knowledge for Spinoza, is mediated by our human body, as he states in IIP26:
The human mind does not perceive any external body as actually existing, except through the idea of the affections of its own body.
Our perception of things at this level, therefore, tells us more about the condition and nature of our own bodies, rather than the nature of external things themselves. Thus if I am short sighted things will be blurred and small, but this is true for human nature in general, since we can only perceive external things in the way that they affect our bodies, and we cannot perceive them in any other way. In Spinoza’s terminology this fundamental relation between the idea and the object mediated by the body is called imagination. When I see something for Spinoza, I am imagining it. This does mean that I am making it up; rather I have an image of it in my mind, whose origin is mediated by the affects of the body. The image is the correlate of the sensations. We should, however, be very careful about what Spinoza means by the word ‘image’ here. An idea is certainly not a picture (as Spinoza makes very clear in IIP43S), if one imagines a picture to be some kind of thing which is a copy of a real thing, as though in the mind there existed images which corresponded to actual things; rather an idea is always a mode of the attribute thought. Error does not happen because I have the image of something in my mind which is wrong; rather error happens because my mind lacks the idea that excludes the existence of the thing that I imagine to be present. Thus, to use Spinoza’s example, when the young child imagines the existence of a winged horse, it is not the image of the ‘winged horse’ that is in error, but the child lacks the knowledge that would tell him or her that this image could not possibly exist. So there is nothing wrong with the imagination in itself, as Spinoza writes in the scholium to IIP17:
For if the mind, while it imagined nonexistent things as present to it, at the same time knew that those things did not exist, it would, of course, attribute this power of imagining to a virtue of its nature, not to a vice.
Inadequate ideas are those ideas which are caused from outside of my mind. This is only a partial knowledge of an object, whereas adequate ideas, within the internal necessity of the order and connection of ideas, are a complete or whole conception of the object. If we only remained within the external relations of the mind to objects, then we would only have a partial and mutilated understanding of the universe. But why is this understanding only partial and mutilated? This is because the body has a negative impact on the causality of ideas, if we assume that we only know things through perception. Thus, I am affected by the rays of the sun as it warms my face. There is nothing in common between me and the sun, and therefore, at this level, I cannot have an adequate idea of the sun. Rather, as we have already said, this relation tells me more about the body affected (in this case myself) than the body which is the cause of the affection. As Deleuze says in his lectures on Spinoza, a fly would be affected by the sun in a different way (Deleuze 1978). The reason why this is inadequate knowledge is that I only know the sun in terms of its effects on my body (just as the fly only knows the sun in terms of the effects on its body) and not in terms of causes; that is to say, what the cause of the sun and what is the cause of the heat on my face and so on. To know that I would have to know what my body was and what the sun was, and I could not know that simply through the effects of one body on another (it is not through the warmth of the sun against my face that I know that my idea of the sun is adequate and the idea of the sun of the fly is not). Inadequate ideas are therefore representation of effects without the knowledge of causes.
The idea of inadequate ideas will become very important in the rest of Spinoza’s Ethics. For to live at the level of the knowledge of effects, that is to know nothing of the causes of things, is to live a life of encounters only. One sensation follows another sensation, but I have no real understanding of the causes of these sensations. This is the level, unfortunately, that most of us live. When we come to think about our ethical life, this means that we are completely under the control of one feeling following another, like a paper boat buffeted by the mighty waves of the ocean of emotion. If we knew the true cause of these emotions, then we would be in control of them, rather than they in control of us. Knowledge of these true causes is the aim of the rest of the parts of the Ethics.
Curley, E., 1988. Behind the Geometrical Method : a Reading of Spinoza’s Ethics, Princeton N.J.: Princeton University Press.
Deleuze, G., 1978. Les Cours de Gilles Deleuze. Sur Spinoza. Available at: http://www.webdeleuze.com/php/texte.php?cle=14&groupe=Spinoza&langue=2 [Accessed September 30, 2012].
Lahn, B.T., 2004. Human Brain Evolution Was a “Special Event.” Available at: http://www.hhmi.org/news/lahn3.html [Accessed November 25, 2012].
 Humans have extraordinarily large and complex brains, even when compared with macaques and other non-human primates. The human brain is several times larger than that of the macaque — even after correcting for body size — and “it is far more complicated in terms of structure (Lahn 2004).
 We can of course improve our bodies in relation to instruments, but these instruments themselves have to relate to what our bodies can interact with. There is no point having a powerful electronic magnetic microscope if we can’t make available to the human eye the images that it produces.