A higher order concept is a concept that is expressed in other phenomena but somehow transcends them. In other words, the whole is more than the sum of the parts. An example is music: it is expressed by means of sounds but is somehow more than just the sounds, it cannot be reduced to them. One of the key problems of philosophy is to understand how higher and lower order phenomena relate to each other. How does music relate to sound, consciousness relate to neurons firing in a brain, or love relate to hormones? In what sense, if any, is the higher order phenomenon more than just the sum of the lower order phenomena of which it is composed?
Any theory of absolutely everything must explain either why and how higher order concepts exist, or why we think they do whereas they in fact don't.
Mainstream science does not offer an explanation as to how a whole can be more than the sum of its parts. If anything, it suggests the reverse. The decomposition of a whole into its constituent parts figures prominently in its toolkit of methods to arrive at an understanding of phenomena. Those who take mainstream science religiously are inclined to take a reductionist standpoint, rejecting categorically that the whole can be anything more than the sum of the parts. This point of view does not correspond with our observation, and must therefore be rejected.
QO has an explanation for why wholes are often more than the sum of the parts, which is based solely on observed quantum mechanical phenomena, and therefore has an Occam score of 0000.