ANT: Latour’s interests are definitively not primarily epistemological, but ontological ones. He does not focus on the nature of knowledge of the world, but tries to figure out the nature of a world in which knowledge plays a role our world, i.e., the world of science and technology.
To get a feel for ANT, think of the world as a staged play. How does an actor become a character in a play? Only by interacting with other actors and with artefacts, and by speaking about himself, artefacts, events, and so on. What character is he? Look for the artefacts and the actors that surround him and the plots he is involved in. Watch how artefacts mediate to define a character: a crown on his head translates an actor into a king, and vice versa. How does a prop become a particular artefact which plays a definite role in the world of the play? Look how it has become involved in interactions.
On stage, each thing is only constituted solely through its interrelations with, and differences from, everything else. Nothing has any intrinsic features of its own. ‘The properties of a thing are effects on other “things”. If I remove all the relationships, all the “properties”, all the “activities” of a thing, the thing does not remain.’ (Is that a Latour quotation? No, but it could have been. In fact, this is Nietzsche). So, to answer any question about what anything is, and to answer any question about meaning, we have to study how the world in which it plays a role is built up as an effect of interactions, i.e., interactions in which both humans and non-humans are involved. We have to deconstruct the ‘scripts’ that brought actors and artefacts into existence, study their genealogy, and see how in that process they became bestowed with essences.
What is the philosophy behind this? First, call to mind the Saussurian idea (commonplace in semiotics) that there are only differences in language: nothing inherently suits a phoneme for its role in words, the only thing that matters is that it differs from other phonemes. (For example, the phoneme b enters in bat and bed, not in rat and red - that makes b into a distinguished phoneme, but nothing inherently affords b this particular role.) ANT follows up on this. It radicalises this idea, by applying the Saussurean principle to the whole world. Interestingly, ANT is not the first to have done this.
In fact, Nietzsche already took - twenty years before Saussure - this step (from which Saussure explicitly refrained) to apply the intuition that language is a system of differences to the whole world. So, what we are talking about is a pan-semiotic ontology, a Nietzschean conception of the world as a text, or - as I would prefer - as a staged play.
http://www.easst.net/review/dec1995/devries by Gerard de Vries