 Αμία names' NOTHIS ψήλος, and professor of philosophy of science and metaphysics in the university of Athens Greece, and a member of the Rotman Field University of University of Western Ontario, Canada. I'm here to talk about scientific realism, that's a philosophical view about science, the thrust of which is at sciences in the truth business. There are various ways to understand and define scientific realism, but my own preferred way is to understand scientific realism as consisting of three philosophical phases, One Metaphysical, one semantic and one epistemic. The Metaphysical thesis says that the world has a definite and mind-independent structure. The semantic thesis is about scientific theories. It says that scientific theories are truth-condition descriptions of the intended domain, hence they are capable of being true or false. The theoretical terms which feature in scientific theories have putative factual reference. So if scientific theories are true, then the unobservable entities, they populate the world. Finally, there is epistemic thesis and the claim that mature and predictably successful scientific theories are well confirmed and approximately true. Hence entities which are posited by scientific theories or at any rate entities very much like those posited in habit the world. You might wonder why three theses about scientific realism. Now the first, the Metaphysical thesis, is meant to make scientific realism distinct from anti-realist accounts of science, be they traditional idealist and phenomenalist accounts or more modern verificationist accounts, a la dame or the middle pattern. What is at stake in this debate? At stake, in my view, is the possibility of divergence between what there is in the world and what is issued as existing by a suitable set of epistemic practices and conditions. The realist commitment to the main independence of the world implies that if the unobservable entities exist, they exist independently of our ability to be in a position to know, verify, recognize, etc. that they do. The second thesis, which might be called semantic realism, makes scientific realism distinct from eliminative instrumentalist and reductive empiricist accounts. Eliminative instrumentalism, a view that was developed in the early 20th century by various philosophers, takes the cash value of scientific theories to be fully captured by what theories say about the observable world. This position typically treats theoretical claims as syntactic mathematical constructs which lack truth conditions, hence they lack any assertory content. They don't say anything about the world really. Reductive empiricism on the other hand treats theoretical discourse as being disguised, talk about observable entities and their actual and impossible behavior. It is consistent with the claim that theoretical assertions have truth values, but understand the truth values reductively. They are fully captured in an observational vocabulary. Opposing these two positions, scientific realism in its semantic stripe, is an ontologically inflationary view, understood realistically the theory admits of a literal interpretation, that is an interpretation in which the world is populated by a host of unobservable entities and processes. So electrons, molecules, DNA molecules or whatever are part and parcel of the furniture of the world according to the scientific realist position. The final element of scientific realism is the epistemic thesis which I call epistemic optimism. It is meant to distinguish scientific realism from agnostic or skeptical versions of empiricism. The thrust of this thesis is that science can and does deliver theoretical truth, no less than it can and does deliver observational truth. So theory does not tell us only about what we see in the world, but it tells us about what we don't see in the world in its unobservable structure and content. It's an implicit part of the realist thesis that the amplitude of abductive methods employed by scientific scientists to arrive at their theoretical beliefs are reliable.