The Kosmos as the previous figure drew it: one thought, four windows. Interiors on the left, exteriors on the right, and each window correlated with the others, which is what makes a reduction tempting.Gross reductionism starts from the same four windows……and reduces all of them to the Upper Right, then reduces the Upper Right to atoms. Wilber's verdict: a few "highly gifted nuts", and "not historically that influential".Subtle reductionism also starts from all four windows, and keeps the whole web of exteriors in view……but reduces every interior to its exterior correlate: I to it, we to its, a thought to a brain state, culture to social integration. The web is whole and nothing is inside it. This is flatland, and in Wilber's telling the Enlightenment's real downside.The settled frame: the Kosmos and its two flattenings side by side, with Wilber's sentences. This is the shareable image.
A sequel to One thought, four windows. Every interior has an exterior correlate, and that is what makes two kinds of reductionism tempting. Gross reductionism reduces everything to the Upper Right and then to atoms. Subtle reductionism keeps the whole interlocking system but collapses every interior into it, so thoughts become brain states and culture becomes social integration. Wilber says the second, not the first, is what built "flatland":
"They don't reduce everything to atoms; they reduce everything in the Left-Hand to a Right-Hand description in the 'system.' They reduce a four-quadrant holism (or Kosmic holism) to merely a Right-Hand holism, a flatland holism."
Ken Wilber, Sex, Ecology, Spirituality (1995), ch. 4
The two reductionisms, their verdicts and their targets are Wilber's. The three grids, the arrows and the web drawing are this wiki's. More: Flatland.