Coming home last night I was thinking about music and why it does me good. Thinking about that made me think about a time when I spent a lot more of my time making and listening to music. I spent a lot of time back then being a lot less happy than I am most of the time now, and I presume the music was necessary.

This is not to say it isn't necessary any more. I've been singing and playing the guitar again recently, and I have realised that one of the symptoms of insufficient music is forgetting how much good music does you. I'll try not to forget again.

It can be tempting to think of music as an emotional affair, a misconception that some people make a lot of money out of. Or to see its sole value in its crystalline abstract beauty, as if there were no passion in Bach. Either view is incomplete. But I think it would be wrong too to see successful music as addressing the intellect and the emotions simultaneously: that would be to make two things out of one.

As I came home last night and thought about the time I spent more time on music, I tried to remember what I was like back then. In principle a hopeless task: our selves are not available for introspection, and even less for retrospection. Nonetheless I felt the illusion of a moment of success, my posture deteriorated, and I remembered or imagined an attitude more than a feeling which left me more vulnerable to the world around me, my mind like a house without a roof where the rain came in and made some things grow and washed others away.

On a longer timescale, I have been thinking about the mind and perception. I read something a few months ago in which someone mentioned the basic problem faced by the idea that our perceptions resemble reality, which is that you can never confirm the resemblance: it is not as if you could compare the perception with the reality itself! I have been thinking about why that is nonsense, and why it is not obviously such.

The implicit image is one of a person looking at a moving picture in their mind and wondering if it is a picture of reality, with nothing more than other moving pictures to judge by. As if our consciousness were stuck in a scale model of Plato's Cave in our heads, or a cinema with no exits.

In fact, the cinema has no screen and there is no image at all. Our perceptions do not resemble reality in any useful sense, and would be of no use if they did. Imagine that our minds constructed an image of the world in our heads: how would we then use that image? We would have to perceive the image in a similar way to the way we perceive the world. (And create another image?)

The temptation to imagine a perception as an image is a side-effect of an excessive concentration on vision. Those of us who are not blind tend to think of reality in visual terms, and it is not immediately nonsensical to imagine wanting to compare a reality conceived in visual terms with our visual perceptions, since we would apparently be comparing like with like. The problem is not, however, that the comparison is impossible, but that the idea of it is nonsensical. Reality is not a vision, although it can be seen.

Consider the other senses. How could a tractor resemble the sound of a tractor? Does garlic resemble its taste? A rose by any other name would not be comparable to the smell of a rose, and what thing might resemble the feeling of the warmth of the sun on your skin? Similarly, it is not a deficiency or a problem with our visual perceptions that their resemblance with reality cannot be confirmed, since there is no sense in which they could meaningfully be claimed to resemble reality, or even resemble an image of it.

In the real world, if we want to check the accuracy of our visual perception of, let us say, a tree, we go up to the tree and look at it from a different angle, smell it, feel it, hear the wind in its leaves, and possibly even taste it (or parts of it). In the doorless cinema image of mind and perception what we are doing is examining a model in our mind, or in a part of our mind – a part that in the 17th Century was referred to as the 'sensorium'. But there is no evidence for the existence of this model, and whatever the mind might do with the results of that investigation it could equally well do with the results of an investigation of the real tree.

Not only does the cinema have no screen, it has no walls. The world itelf is the sensorium. We do not passively face a model in our minds with no indication of where it came from, but actively explore the world that moves us. That truly moves us: action requires motivation, and therefore emotion: at the root of our intellectual comprehension of the world is our emotional engagement with it. It can please us and it can hurt us: the cinema has no roof either, the rain comes in and makes things grow.

Given the risks of interaction with a dangerous world, it is understandable if people at some point remain content with the things they have learned and build a roof over their lives to keep the rain out. It is possible to create a kind of model in the mind, representing those parts of reality we need to cope with the routine of a protected life, and to let things dry out in safety. Emotion is confined to desiring the attained, intellect to maintaining it.

The appreciation and creation of music demand that what would thus be channelled and separated remains whole and alive. It can be abused for temporary relief in an otherwise intolerable life. Or it can help us knock the walls down before they are built, blow off the roof, let the rain in and let things grow.