PSIM describes what Sellars sees as the major problem confronting philosophy today. This is the “clash” between “the ‘manifest’ image of man-in-the-world” and “the scientific image.” These two ‘images’ are idealizations of distinct conceptual frameworks in terms of which humans conceive of the world and their place in it. Sellars characterizes the manifest image as “the framework in terms of which man came to be aware of himself as man-in-the-world” (PSIM, in SPR: 6; in ISR: 374), but it is, more broadly, the framework in terms of which we ordinarily observe and explain our world. The fundamental objects of the manifest image are persons and things, with emphasis on persons, which puts normativity and reason at center stage. According to the manifest image, people think and they do things for reasons, and both of these “can occur only within a framework of conceptual thinking in terms of which [they] can be criticized, supported, refuted, in short, evaluated” (PSIM, in SPR: 6; in ISR: 374). In the manifest image persons are very different from mere things; how and why normative assessments apply to things is an important and contentious question within the framework.
The manifest image is not fixed or static; it can be refined both empirically and categorically. Empirical refinement by correlational induction results in ever better observation-level generalizations about the world. Categorial refinement consists in adding, subtracting, or reconceptualizing the basic objects recognized in the image, e.g., worrying about whether persons are best thought of in hylomorphic or dualistic categories or how things differ from persons. Thus, the manifest image is neither unscientific nor anti-scientific. It is, however, methodologically more promiscuous and often less rigorous than institutionalized science. Traditional philosophy, philosophia perennis, endorses the manifest image as real and attempts to understand its structure.
One kind of categorial change, however, is excluded from the manifest image by stipulation: the addition to the framework of new concepts of basic objects by means of theoretical postulation. This is the move Sellars stipulates to be definitive of the scientific image. Science, by postulating new kinds of basic entities (e.g., subatomic particles, fields, collapsing packets of probability waves), slowly constructs a new framework that claims to be a complete description and explanation of the world and its processes. The scientific image grows out of and is methodologically posterior to the manifest image, which provides the initial framework in which science is nurtured, but Sellars claims that “the scientific image presents itself as a rival image. From its point of view the manifest image on which it rests is an ‘inadequate’ but pragmatically useful likeness of a reality which first finds its adequate (in principle) likeness in the scientific image” (PSIM, in SPR: 20; in ISR: 388).
Is it possible to reconcile these two images? Could manifest objects reduce to systems of imperceptible scientific objects? Are manifest objects ultimately real, scientific objects merely abstract constructions valuable for the prediction and control of manifest objects? Or are manifest objects appearances to human minds of a reality constituted by systems of imperceptible particles? Sellars opts for the third alternative. The manifest image is, in his view, a phenomenal realm à la Kant, but science, at its Peircean ideal conclusion, reveals things as they are in themselves. Despite what Sellars calls “the primacy of the scientific image”(PSIM, in SPR: 32; in ISR: 400), he ultimately argues for a “synoptic vision” in which the descriptive and explanatory resources of the scientific image are united with the “language of community and individual intentions,” which “provide[s] the ambience of principles and standards (above all, those which make meaningful discourse and rationality itself possible) within which we live our own individual lives” (PSIM, in SPR: 40; in ISR: 408).