 It is perhaps only a slight exaggeration to say that scientific realism is characterized differently by every author who discusses it, and this presents a challenge to anyone hoping to learn what it is. Fortunately, underlying the many idiosyncratic qualifications and variants of the position, there is a common core of ideas, typified by an epistemically positive attitude toward the outputs of scientific investigation, regarding both observable and unobservable aspects of the world. The distinction here between the observable and the unobservable reflects human sensory capabilities: the observable is that which can, under favorable conditions, be perceived using the unaided senses (for example, planets and platypuses); the unobservable is that which cannot be detected this way (for example, proteins and protons). This is to privilege vision merely for terminological convenience, and differs from scientific conceptions of observability, which generally extend to things that are detectable using instruments (Shapere 1982). The distinction itself has been problematized (Maxwell 1962; Churchland 1985; Musgrave 1985; Dicken &amp; Lipton 2006) and defended (Muller 2004, 2005; cf. Turner 2007 regarding the distant past). If it is problematic, this is arguably a concern primarily for certain forms of antirealism, which adopt an epistemically positive attitude only with respect to the observable. It is not ultimately a concern for scientific realism, which does not discriminate epistemically between observables and unobservables per se.