Thinking about what we mean by our words for kinds of things (“lions”, “gold”, “trees”, etc…), it seems clear to me that what we have in mind are not some essences. (This is of course separate issue from the issue if in fact the individuals which we see as belonging to the certain kind in fact share some essential characteristic.)
It can’t be that we have the essence in mind, because we aren’t aware of this essence. We can for sure think of “the essence which is shared by all those things” without knowing it, but even before that we need to have “those things” in mind in first place. Some kind of grouping of things into a kind needs to be done even before common essential characteristic is assumed.
So, given that it is not some essential (or defining) characteristic that is base of seeing individuals as belonging to one kind, what is it?
Last year, I was saying that it is some similarity on base of which we see individuals belonging to some kind – that is… we become aware of group (multitude) of individuals sharing some similarity, and it is that what we have in mind (the multitude of individuals [actual or possible] sharing some similarity) and that we baptize that when we introduce common nouns. So, to say – there happens to exist this multitude of things which are similar in some way, and we think of them when we use those common nouns. Be it the case where we talk about lions, trees, water etc…
As part of this kind of stance, in other posts I said I’m suspecting that there aren’t such things as concepts – e.g. LION, WATER, TREE, which would be what is meant by our common nouns. That is because, first I think the basis of using common nouns is in thinking of multiplicity and not of one single thing which has some properties; and second because that what we refer to are groups of things which happen to exist (that is what we have in mind) – we don’t have in mind some abstract criteria.
I think there is another part for this my story to make sense – and those are the gaps in the “similarity space”. If we put attention on the things that happen to exist, even if we can’t specify some defining characteristics of them, it so happens that there are gaps in their similarity. That is, it so happens that we have lions which are similar to each other, and then we have a gap of similarity to some other species. It is this fact, I think, that even in the absence of defining features, enables us to think of kinds of things – so it happens that there are not individuals which would fall in the similarity space between lions and e.g. tigers.
Of course, there might happen to be one individual (something between a tiger and a lion) but that wouldn’t really mean that there are no two groups of individuals which are separated by a gap. It would be two groups and one individual between them. But if instead of this individual, there happened to be lot of individuals which would fill the similarity gap between tigers and lions, it is hard to imagine that we would be able to discuss two kinds of things as we are today. What we could do is maybe paying attention on some feature, and do arbitrary setting of some border, but that would be quite different I think.
Because our thinking of lions and tigers as two different kinds today IS based on the fact that there is a real gap, not of our making, and that we have in fact group of things which are similar among each other. It is this actual phenomenon that we are thinking of. So, while there are no defining features, and even no defined borders of when does a lion stop being lion (and becoming something else), there is a real phenomenon. While in the case where we would arbitrarily define what would be counted as lion, we are moving in thinking about quite another thing. We are not thinking of things which happen to exist, but we are defining kinds based on features – and this kind of definition is unrelated to the issue if individuals exist which satisfy this feature or not.