I thought I'd share something that was very helpful for me to understand the Marxian idea of Homo Faber or the idea of humans as the tool-making animal.
Although we take for granted the notions that the mathematical formula for pi= 3.1415... or that if you plant a seed in the ground that a plant will grow from it or even that we can use words to communicate these tools didn't always exist.
The question is where did they come from?
Rationalist philosophers before Kant would posit a metaphysical world and a rational essence in humans which accesses that world.
Dialectical materialists like Marx take Kant's critique of 'pure reason' or metaphysics and take it one step further to say that these 'ideas' come into being as praxis or habits.
A person in a primitive tribe doesn't suddenly decide one day that it's better to plant a garden then it is to gather food all day. How does he know that seeds turn into plants? Do we imagine that he is paying a lot of attention to his environment and just figures it out? If that is so, why did technology appear so slowly throughout human history?
Instead as Roheim points out, these things are based upon unconscious phantasy which later received a rationalization and is given another use.
It may be 'natural', that is, phylogenetically pre-determined, for man to kill and eat animals or gather and eat berries, but it is certainly not 'natural' for primitive man to plant a garden or to domesticate animals. If we analyse the 'professions', apart from those of the hunter, the fisher and the gatherer of wild plants, we find that the most ancient of all professions is that of the medicine man. This is followed by trade and later by primitive agriculture, then the domestication of animals and finally plough culture. All these can only be explained as based on sublimations of specific aspects of the infantile situation. It shows very little insight into the mental processes of primitive man to believe that he is likely to plant yams because he has come to the conclusion that they will bring him a plentiful crop in the future, or that he keeps dogs because they are useful in hunting kangaroos. The carefree children of the jungle or desert never think of the morrow in pre-agricultural societies. But if they have associated phantasies of destroying the body with taking the yams out of Mother Earth, it would be easy to see how the reparation aspect of those phantasies might lead to a replanting, that this in turn might lead to an observation of the crop, and so secondarily to a practical result from the endopsychically conditioned activity. Or, if man extended the mother-child situation to the puppy of the wild dog, these dogs, brought up in human society, might prove useful in the chase; but this was a result of a play activity which nobody could have foreseen. My view, therefore, is that the bulk of human culture, even in its adaptational or ego-aspects, arises out of play or ritual activities. The reason for these activities lies in the infantile situation, and they acquire survival value secondarily by assimilating a part of the environment to man's needs. This is the way of culture—the transformation of id into ego. (Roheim, The Psychoanalytic Interpretation of Culture, p.162-3).
the id is transformed into habits or praxis of which we can't give a conscious justification.
I can't tell you why 2+2=4. I simply memorized it and other small sums. With bigger numbers I was taught the praxis of carrying the 1 when I added, and the reason I know this is right is because everyone else does the same thing and there is no other way to do it. It's not because my rational soul knows the essence of the numbers because if it did then why do I have to force myself to memorize small sums and how to calculate big ones?
This isn't post-modernism. There aren't any tribes who have different mathematics than us. They either don't have any arithmetic (there are tribes that only count up to 5) or they have arithmetic like us (although they have different words or a different number base we'd have to learn).
It's the same thing with pi. Egyptians just took triangles and tried to see how many they could put into a circle and that is how pi was originally calculated.
And, with language we have to imagine that feelings like love and jealousy emerged in humans (the 3rd Chimpanzee) and that language was motivated from the desire to know what the beloved did when you were parted (so the unconscious symbiotic fantasy could continue) or out of jealousy of the attention shown to another and fear of attacking him, one begins to study the other's behaviour. Language too would arise very slowly.
The ego ideals, within the superego, are more intimately tied to the id than to the ego. We are 'driven' to get recognition or find love as much as we may be driven orally, for example, to want to chew gum even though it has no nutritional value, or smoke to stimulate the respiratory system, etc.
We use practical reason to go after our ideals and our id impulses. Our desires lead us and, as Roheim points out, we also create because we play. Practical reason is the secondary movement and not the leading one as philosophy would have it.