From his book Integral Psychology:
The most pervasive notion in human history and prehistory (namely, the existence of some sort of spiritual dimension) was simply pronounced, with the thundering authority of science, put with a zeal that was inversely proportional to its believability, to be a massive collective hallucination. The spiritual dimension, it was solemnly announced, was nothing but a wish-fulfillment of intantile needs (Freud), an opaque ideology for oppressing the masses (Marx), or a projection of human potentials (Feuerbach). Spirituality is thus a deep confusion that apparently plagued humanity for approximately a million years, until just recently, a mere few centuries ago, when modernity pledged allegiance to sensory science, and then promptly decided that the entire world contained nothing but matter, period.The bleakness of the modern scientific proclamation is chilling. In that extraordinary journey from matter to body to mind to soul to spirit, scientific materialism halted the journey at the very first stage, and proclaimed all subsequent developments to be nothing but arrangements of frisky dirt. Why this dirt would get right up and eventually start writing poetry was not explained. Or rather, it was explained by dumb chance and dumb selection, as if two dumbs would make a Shakespeare. The sensorymotor realm was proclaimed the only real realm, and it soon came to pass that mental health would be defined as adaptation to that "reality." Any consciousness that saw something other than matter was obviously hallucinating.
If there is ever to be a truly integral psychology (or any sort of integral studies), this extraordinary rupture between premodernity and modernity--spiritual and material--needs to be confronted head on. Although there is a slow movement in the modern and postmodern world to reintroduce some sort of spirirtuality, nonetheless the "official" and most widespread worldview of the modern West is that of scientific materialism. And clearly, we cannot have an integral view of the levels of consciousness if modernity and modern science denies the existence of most of them. "Integral" means, if it means anything, the integration of all that is given to humanity; and if modernity insists instead on trashing everything that came before it, then the integral enterprise is derailed from the start. At the same time, it will do no good, as Romantics wish, to attempt a return to yesteryear, an attempt to "resurrect" the past with a "resurgence of the real," for modernity brought its own important truths and profound insights, which need to be harmonized as well; and yesteryear, full truth be told, just wasn't all that swell."