Lebenswelt is the world we live in, but we've been deceived into thinking that the world which science pictures is the real world. It is a bit like those who refer to the after-college world as the "real world." Where do they think you are living now? The world of science is a colorless world of charged particles (or waves, since scientists can't make up their mind). This room isn't made up of table and chairs, but of clusters, more or less dense, of electrons, protons and a hundred other subatomic particles which can't be seen. There are no values, no meaning, no tastes or beauty in the world; all the interesting properties are subjective. Ask yourself, how did we get convinced of this. Think how contrary this is to ordinary experience. Aren't the trees themselves colorful in the fall; isn't the scene itself beautiful? Even many scientists have become skeptical of the view that scientists tell us what the world is really like; they have been led to taking a purely instrumental view of scientific theories. Theories are mere calculating devices which don't describe anything; they are mathematical formulas which are useful for certain purposes, but they do not depict things in the world.
In the lived world, things are tools - a set if functions. We deal with things as items to be used for human purposes. Sartre himself distinguishes between the en-soi and the pour-soi, but close reading shows how his project differs from Descartes (splitting the world between the world of spirit and the world of science and math, thereby saving religion.) Sartre follows Heidegger, the world of objects never appear to me as mere things; they are presented as tools, or equipment, as items-with-a-use. One way of getting a handle of this view is to recall coming across an artifact which you've never seen before and have no idea what it could possibly be used for. You stare at it, perhaps you turn it around and upside down; it takes on a strangeness. It seems alien.
The pour-soi too is not the passive perceiver or observer of empiricism; we are actors in the world. We are not just "subjects" of knowledge, we are doers-in-the world. As Levy reminds us, we are engaged (in the full sense of the word) in the world, and entities "..have a place in our projects before they are extended matter." (16) Now we do have a good deal of agreement about objects, but that is because humans do have a common biology and therefore share some basic concerns about surviving, and we are born into a social world which has a structure of meanings. Still, we are always aware of the world from a perspective; there is no such thing as a "view from nowhere." Our attention and interests are always behind how the world is cut up and categorized. Levy quotes Sartre:
The point of view of pure knowledge is contradictory; there is only the point of view of engaged knowledge. This amounts to saying that knowledge and action are only two abstract aspects of an original concrete relation. (20)
This is a bit overstated since we do have moments when we take an objectivist view of things; in fact that's what happens to Roquentin in Nausea. He begins to look at things as purely existing, instead of part of a structure. Notice that Roquentin himself is disengaged, and as he becomes more disengaged he not only cannot do anything (e.g., write his biography) he isn't linked into the world enough to make sense of the most trivial of things. The world become an alien world of alien objects. Even the objective view of the world has its uses, but it presupposes the lived world of experience and meaning.
Levy believes that Sartre seems to make the very objectivist mistake which he has criticized; indeed it seems to me that there is an inconsistency between his view that we encounter a world of meanings (the social world) and his view that the en soi, the in-itelf is fundamentally meaningless. That is, there are many passages in which it seems that he wants to insist that meaning comes to the world only with the pour soi. Maybe he can get out of this by saying that meanings have their origin in us, but they are NOT mere projections on the world. They are not subjective in the sense that we could "strip them away." The world is a perspectival world! That is, there is no such thing as a world or a description without any perspective at all. (Levy, 34)
As I have said, Nausea, seems to be a novel about how Roquentin begans to see things in the world as en soi. Maybe, like Wittgenstein in the Tractatus, Sartre is using a novel to showus what cannot really be done. Roquentin's world is doubly a fictional world; the novel itself is fictional and his fictional world is fictional. The novel is strange, indeed it is like science fiction, precisely because Roquentin's world is not our world, and in a sense it isn't even a possible world.
Here is another way that one might defend Sartre. It isn't clear that we ever totally succeed in experiencing a thing as a pure en soi. Similarly, much as we try, we never do quite succeed in turning the other, or ourselves, into an object. We can try to deny our freedom or the other's freedom, but we just can't pull it off. Here Sartre makes use of the notion of the slimy, the vicuous, fleshiness, that which is not quite solid, like a thing, but not free either. This is especially true of persons. We can treat them badly, we can use them for our own purposes completely ignoring their wishes, but can we actually completely treat them as objects?
Not for the tender minded.
My father died very suddenly at the age of 62; at the time I was 36. He was a long way, and among the things going through my head as I flew to Texas was, "Maybe it is all a mistake; maybe he didn't really die." At the funeral home, I felt compelled to touch him, to make sure. It is a most startling experience. Dead flesh is not just cold flesh; it is lifeless. The person has become an object in a profound sense.
We talk these days of treating someone as an object, a sex object, but what does this mean? Does it mean that we treat them like a corpse, like a rock? I don't think so. It may not be admirable to see a person as having only one function or purpose, e.g., sex. Still, it is as a person that they are being so used or so regarded. There is some difference in treating a person as if they have only one function (maid, wage earner, tackling machine, waiter) and treating them as inert matter.