One way to try to get to grips with a tricky term like consciousness is to look at its opposite, to identify what it definitely is not .

It seems that when we look around us some of the things in the world have consciousness and some do not. Human beings seem to have consciousness and probably animals too and perhaps all living things. But do all animals? Dogs and dolphins? Yes. Horses, cats, pigs, chimpanzees? Yes. What about worms, insects, caterpillars? Possibly. And bacteria and viruses? Probably not. As for trees and plants - very unlikely. You will have noticed that the responses above have not been justified at all. I have just given instant impressions without reflecting whether they are true or not. It needs explaining why I feel convinced that human beings have minds, why I am fairly sure that certain animals have minds and much more doubtful about other animals and vegetation?

Again I am simply taking for granted everyday beliefs – just the sort of thing, of course, that philosophy takes apart and analyses. So let us question these beliefs and see if they stand up to examination. When we say that human beings and animals have consciousness we separate them from non-animals, things which are inanimate. No one suggests that inanimate things like stones and bricks, or grains of sand and mountains have minds. Or that motor cycles have minds. (Sometimes it is suggested that computers have or one day might have minds and that possibility certainly nees to be considered.) But first back to a clear-cut example of something without consciousness. When we call stones, bricks, grains of sand and mountains bits of matter, what we mean is that they are summed up in that description. There is nothing about them that gives us the slightest inclination to attribute to them anything that is not physical. Let us for the moment accept this assumption, that there is a difference, at one extreme, between human beings who certainly do have consciousness and, at the other extreme, mountains which certainly do not have consciousness. This approach leaves unanswered and puts on one side questions about which animals if any have minds and whether computers have minds.

Let’s attempt a more straightforward distinction first. We think of minds as being in some way different from physical objects. But what essentially do we mean by the term ‘physical object’? What defines a physical object is that it is extended and being extended means that it fills up a bit of space in the universe. A physical object, whether it is a massive star or a miniscule atom, has a place, a location in space. It takes up a piece of space that has boundaries; it is either at rest or in motion and is either beside or near to or far from other physical objects. Another way of describing extension is to say that an extended thing, a physical object has dimensions. It doesn’t of course matter whether we measure these dimension in inches, centimetres, pounds or kilograms. If you think of a physical object, you think of something that is spatially located and has dimensions.








In ordinary language we make a distinction between knowing directly and indirectly. For example, we know a friend directly but a friend of a friend indirectly, a film directly if we have watched it but indirectly if we have just heard or read about it. Direct knowledge is immediate; indirect knowledge involves an intermediary; it is at a distance and known by means of something which acts as a means or a stage between us and the object of knowledge.

We know the experience of being in pain, of having a toothache or being kicked on the shin, directly. What does it mean to say ‘directly’ like this? By knowing directly, we mean that there is nothing between us and the pain; the pain is not like something we infer from evidence; the pain is an immediate experience. We can say of pain that we do not experience it at second hand; in the case of the pains of other people we are in a different, an indirect relationship; we hear people cry out or see them wince or listen to their accounts of being in pain and from this evidence we infer that they are in pain. Our own pains are not known like this; we know them from a first-person point of view.

If my knowledge of being in pain were based on some intermediary evidence, then I could refer to that evidence and explain how I came to know that I was in pain. But it seems absurd even to ask someone, ‘How do you know that you are in pain? Show me the evidence’. (And equally absurd to reply, ‘I know that I am in pain because I saw someone kick me on the shin and from that observation, I infer that I am in pain’.) Pain is just not the sort of thing that depends on evidence.

Back to the toothache. It is important to distinguish between the experience of the toothache and the cause of the toothache. The former is directly and immediately known; the latter is indirectly known as it is based on evidence and beliefs about such ideas as the reliability of the science of dentistry.

Another approach to the idea of direct as opposed to indirect knowledge is through the example of representative realism. According to this theory (of knowledge of the external world), we know the sense data that exists in our minds directly but the physical objects of which they are representations only indirectly. What we directly experience is, say, a visual image in the mind of a tree; this visual image is a representation of but not the same thing as the tree which exists outside me. Thus we know the experience directly without any intermediary but we know the physical object, the tree, indirectly, that is, through the intermediary of the mental state.

The general claim being made here is that being the object of direct knowledge is a quality of consciousness and that this quality distinguishes conscious states from physical objects which are the object of indirect knowledge.


Conscious states exist in the privacy of an individual’s mind; that individual has to those states a privileged access that is denied to others. It seems an obvious fact that only I know what my ache is like and that I cannot give to anyone else the experience of that ache as I experience it; the best I can do is try describe it to another person, as I might to a doctor; but he cannot experience it for himself in the way that I can. Now, private conscious states like aches and pains and other sensations seem to be very different from public things. For example, I might not be able to share my ache with a doctor but I can show him a rash on my elbow. A rash is, by contrast to an ache, open to public view; anyone can see it, me, my doctor, someone peering through the surgery window; I could even take a photograph of it and send it around the world by email. It is not restricted to my privileged access in the way that my ache is. Thoughts and ideas, memories and emotions, the sensations of hearing, smelling and so on are all experienced from this private first-person viewpoint whereas trees and rashes on the skin, mountains and planets and all physical objects are open to public view. For these reasons privileged access or privacy is considered to be a characteristic of consciousness not shared by physical objects which are publicly accessible.


To talk about the infallibility of conscious states is to assert that we cannot be mistaken about them. If you believe you are in pain, you cannot be wrong; you can misunderstand some evidence and make an erroneous inference from it (see above, DIRECT KNOWLEDGE); for example, you might mistake the ring of a telephone on a television programme for the sound of your own telephone but you could not mistake being in pain for anything else. Suppose a person believed that he was in pain but a series of very experienced doctors could find nothing wrong with him. Their inability to find a medical cause of his pain would not show in any way that he was not experiencing pain. Only I know whether or not I am in pain. Similarly, only you know whether you are or are not in pain. Each of us is an infallible authority (i.e., we cannot be wrong) on these questions. Conversely, if you are in pain, you must know that you are in pain. This claim means that you cannot have a pain without knowing it, that there cannot be any unknown pains. Just as a person cannot be wrong if he believes that he is experiencing pain even when there is no sign of pain behaviour (like crying out or wincing) and doctors can find no medical cause of pain, conversely, if despite evidence damage to the body, like lacerations or burns, the subject affirms that he feels no pain, then he is the infallible authority on this question, the non-existence of pain and he is incorrigible too in the sense that no one else is in a position to correct him. The only pains that there can be are experienced; there can by definition be no unconscious pains. <


The defining characteristic of physical objects is extension, i.e., every physical abject occupies a certain amount of space which has dimensions such as length, breadth, mass, volume. Conscious states by contrast seem not to be spatial, not to be things that occupy a quantity of space. For example, it seems absurd to enquire about the measurements of the experience of a smell or of the mass of a thought or of the volume of an angry feeling. The fact that we talk of physical objects in terms of extension but find it difficult to say the least to talk of conscious states in these terms is considered to be another point of difference.


(In its philosophical sense intentionality is not connected with the ordinary usage of the words ‘intention’ or ‘intentional’.) Intentionality is usually brought into discussions of the distinction between the mind and the physical. But the case that is made for this distinction applies fully to the distinction between consciousness and the physical. The philosopher Franz Brentano (1838-1917) put forward the following distinction between the mental and the physical. To claim that mental states are intentional is to say that mental states unlike physical objects have the property of being about something, that they have a content of some kind. What does this mean? When we are in an angry mental state, our anger is about something, for example, the train nor arriving on time; when we are in the mental state of hoping, our hope is about something, for example, that it will not rain on the wedding day. And so on. Memories, fears, anxieties, ideas, plans etc. all have the property of being about something. By contrast, physical objects lack this property. It is difficult to make any sense of the idea that a mountain, a table, a horse are about something.



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