Good intro. The content is pretty basic and assumes no knowledge. It addresses these basic questions from a materialist, realist, dialectical point of view. This implies:
- unity of subject and object. Consciousness is a state of matter.
- non-reductionism (though what this entails is hardly developed).
- motion is the mode of existence of matter. contradictions are the sources of motion (what exactly this means is not really developed).
- relations are not external to a body, but constitute and determine it.
- (hence) truth is concrete, the totality and not the thing-in-itself is the end goal of knowledge.
- appearances are the non-contingent manifestation of reality. They are not identical and not a veil.
- pratice is the ultimate criterion of truth.
From these principles follow all the following:
- The argument from illusion (e.g., brain in a vat) is intelligently addressed. All sensations reveal something real about the world. If our brain is in a vat, our experiences reveal brain impulses (and the motives of the evil scientist, and maybe more). Nothing a priori prevents us from expanding that knowledge of reality though further interaction with those experiences (Truman Show style). We may be very mistaken, but we can not be. This is enough for realism. (Also applies to dreams and stuff)
- Only a correspondance theory of truth makes sense; practicality is a consequence of truth, and particular disdain for coherence theories for their detatchment from reality.
- The empiricists (naïve materialism) flatten reality to experiences, which allows for Berkeley's idealism to creep in. The connection between appearance and reality is given by practice (hence salvaging realism from Kant's ghost), and the fact that they are not identical salvages materialism (by avoiding Berkeley's ghost).
- The argument from social relativism simply transforms the categories of knowledge put forward by Kant into social categories. Since all (most) our perception is theory ladden, knowledge is hopeless, it is always polluted. The social mediation of knowledge is true, but this is not pollution. Social categories are like a lense, where they may refract and distort or they may augment and reveal. Regardless, the underlying reality comes through. Also, practice.
These are, overall, solid points.
I am critical of certain aspects of the book. It seemed to me that he a priori dismisses (or at least does not affirm) the possibility of absolute truth, which is at odds with his (correct) statement that there are no a priori foundations for knowledge. Then, as much effort as Sayers make to demistify expressions like 'contradiction' and 'unity of opposites', I do not think he suceeds. These formulas are only helful insofar as the meaning is clear, and in here they are not. I think it is possible to demistify Hegel, but he often fails. Due to this there are more than one outrageous takes throughout.
I do appreciate his historical approach to philosophy. He grounds the position he discusses (supports or criticizes) well, with very relevant quotes from Locke, Hegel, Marx, Hume, Berkeley, Kant, and others.