The appeal of the Given is that it promises a point at which the regress of justification terminates: my belief that there is a cup before me is justified by my perceptual experience, and my experience is not itself something I need to justify — it is simply given, directly present, self-evidently the case. This picture of experience as a non-conceptual bedrock seems to secure empirical thought against the charge that it floats free of reality — it gives thought a grip on the world through the bare causal impact of the world on the senses.
McDowell argues, following Sellars, that the Given fails precisely at the point where it was supposed to deliver. If the content of experience is genuinely non-conceptual — if it is bare sensory impact, prior to any application of concepts — then it cannot stand in a rational relation to any conceptual claim. A cause is not a reason. The unconceptualised impact of light on the retina does not, by itself, justify the belief that there is a cup before me: to get from impact to justified belief, I need to apply concepts, and the moment I do, the Given has been conceptualised and is no longer bare. The Given generates a dilemma: either it is non-conceptual, in which case it cannot justify; or it is conceptualised, in which case it is not a bedrock.
McDowell diagnoses a systematic oscillation in modern epistemology between the Myth of the Given and an equally unacceptable alternative: coherentism. When the Given is abandoned, thought seems to have no external anchor — it can spin in a coherent void, without genuine contact with the mind-independent world. This is the "frictionless spinning in a void" that McDowell finds in Davidson's coherentism. Philosophy then swings back to the Given to restore external constraint, only to face the problem that the Given cannot rationally constrain. The task is to find a position that escapes both oscillations.
The Myth of the Given is analysed in Lectures I and II of Mind and World (1994), drawing on Wilfrid Sellars's "Empiricism and the Philosophy of Mind" (1956). McDowell's diagnosis extends Sellars's critique by tracing the oscillation to a defective picture of nature.