 A different sort of problem with the actualist version of higher-order thought theory relates to the huge number of thoughts that would have to be caused by any given phenomenally conscious experience. (This is the analogue of the ‘computational complexity’ objection to inner-sense theory, sketched in section 3 above). Consider just how rich and detailed a conscious experience can be. It would seem that there can be an immense amount of which we can be consciously aware at any one time. Imagine looking down on a city from a window high up in a tower-block, for example. In such a case you can have phenomenally conscious percepts of a complex distribution of trees, roads, and buildings; colors on the ground and in the sky above; moving cars and pedestrians; and so on. And you can—it seems—be conscious of all of this simultaneously. According to actualist HOT theory, then, it seems you would need to have a distinct activated HOT for each distinct aspect of your experience—either that, or just a few such thoughts with immensely complex contents. Either way, the objection is the same. For it seems implausible that all of this higher-order activity should be taking place (albeit non-consciously) every time someone is the subject of a complex conscious experience. What would be the point? And think of the amount of cognitive/neural space that these thoughts would take up! (In contrast, we know that neural tissue and activity are expensive; see Aiello and Wheeler 1995; and we also know that as a result of such constraints, the wiring diagram for the brain is about as efficient as it is possible for it to be; see Cherniak et al. 2004.)