I presuppose a connection and interaction between our understanding of things (abstract concepts) and our living in the world or experiencing the world (the concrete). So the world we live our everyday lives in is always the world of the concrete mixed with the abstract and the world we ‘think in’ is the world of the concept mixed with the concrete.
On no level can those worlds truly be separated, they always interact and influence each other. Therefore there is no truly immediate perception or an absolutely abstract concept. Every perception has at least some element of mediation through the logos (language, concepts, knowledege, Vernunft) and every concept has at least some element of experience it is based on or derived from (this is the idea of the concrete within the universal or sublation). Western thought now has the tendency to emphasize and analyze just one of those levels. It tends to look at the universal and sees the concrete as secondary in respect to knowledge. We have seen that abstraction can lead us to amazing discoveries and is a very powerful tool to understand the world.
Therefore there has been an ever increasing tendency to look just at the concept and treat the concept as if the world we live in was no different from the concepts that describe it. We say that the important parts of the concrete are sublated in those concepts and therefore looking at the concrete won’t give us any more useful information than we already have, if we have understood the concept fully. So why do I bother with the concrete at all? Because, as we all know, there is a difference between understanding and doing something, there is a difference between the theoretical and the practical. We make theories about things and expect those things in the world to behave according to that theory, but that only works in theory. If you talk to construction workers or people working in applied physics, they will tell you that there is a difference between the way things work in concepts and the workings of the world. By only focussing on the level of theory we tend to forget about this difference.
This way of thinking Whitehead calls the fallacy of misplaced concreteness. There is an aspect of the concrete world (and our experience of it) theory cannot grasp, precisely because theory is abstract. Think about a concrete experience, lets say you see an apple on a table. In one glance you can grasp the relation of one to the other, whether the colors match, if it is the same apple as yesterday, the style and so on. (notice here that I am not saying that you do not need any knowledge to be able to do this, I am just saying that applying your knowledge in this way gets you more data than just the concepts ‘apple’ and ‘table’ and their relation ‘on’) The concrete experience has given you an awful lot of information that can not adequately be put in words. (By that I mean that I need an awful lot of words to explain what we see in one glance). Why is that? Because of the way abstraction and therefore language works.
Abstraction has to leave something out. Usually in abstracting we try to leave the irrelevant bits of information out. But who can tell what is going to be relevant in the future? How can we decide a priori what is necessary in one occurrence (the essence) and what is just accidental? Doesn’t that depend on the question I ask? So if we just stick with the abstract then we might miss something relevant for our question, just because those data didn’t seem important to the people that defined the object we are inquiring about. So if we want to know whether the shade of red of the apple matches the table, we can not use the classical definitions of ‘apple’ and ‘table’ because they don’t tell us anything about colours.
Where does that leave us? Should we leave the realm of language and thought behind in favor of an unutterable experience? I think not. But we should take into consideration that there is more to life, than we can put in words. And therefore it is always interesting to start anew from the concrete.