If we think of the human mind, it is a very elaborate structure and so it is hard to see clearly the foundation of the structure. People have thought that the mind was a device for solving logical problems, or for living socially with others, or for predicting the future, or for creating new things… How you judge a mind depends on where you are coming from in terms of the ‘what is it for?’ question.
Let’s follow the clues from a biological point of view. The simplest thing with some weensy, teensy whiff of mind-like something is a free-living, single-celled creature that moves. It has two of the characteristics of life, mobility and irritability, among the others. These two seem to go together; the more the mobility, the more the irritability; the less of one, the less of the other. These little creatures can sense which side of them is warmer, or more lit, or has more nutrients, or has less poison. Having sensed a difference, the organism can move along the gradients, attracted by some things and repelled by others. All cells have this ability to some extent whether they are free-living or part of a multicellular organism.
As soon as we have multicellular organisms, there is a tendency for cells to specialize. Some take over the duty of digestion, some of respiration, some of elimination, some of reproduction and so on including irritability and mobility. All the cells retain at least some ability at all the characteristics of cells but specialize in a narrower range. They form organs with different functions contributing to the well-being of the whole organism. The mobility function is taken over by primitive muscle cells and the irritability function is taken over by primitive sensing cells. The sense cell senses something and communicates this directly to the muscle cell. There is no more mind here then in the free-living cell very, very, very little. The organism senses the environment and reacts to it in an absolutely fixed manner.
Now we add neurons connecting the sensing cells to the acting cells. Even the first layers of inter-neurons make a difference; they allow rhythms of action, patterns of action, sensing of patterns and simple learning. The synapses in the pathways between sensing and doing allow processing. As the number of inter-neurons increases, the sophistication of processing increases.
Layers take on different tasks. A predator would have layers of neurons that integrated sensory signals to recognize the pattern of the animal’s prey. Others might track the direction of moving prey. Others choose patterns of muscle movements and so on. So a toad will flick its tongue out and catch a fly that flies too close by. This is a very stereotypical action, almost reflexive, but it does imply an operational concept of a fly object and of a flick of the tongue action. To that extent they are elements in a rudimentary model of the environment and the animals interaction with it.
More layers of neurons allow action that is less stereotypic. An animal that finds and tracks its prey, sneaks up on it and picks the right moment to spring, has to have a very elaborate model of itself in its environment. The animal must have a goal and a plan. It must predict outcomes. It must have an integrated picture of the world and itself in it. It must have memories of events and have learned from those memories. By this level of neuron layers between the senses and the muscles, we have consciousness although perhaps we do not have full self-consciousness until we add the need to work in a social group.
The roots of mind go back to very primitive organism and it was built on the foundation of movement. What is it for? It is for successful behaviour. Its for knowing where you stand and where you will land before you decide to jump.