the house not directly seen, like the size and shape of its other sides. This process is sometimes referred to as apperception. These expectations resemble judgments and can be wrong. This would be the case when it turns out upon walking around the "house" that it is no house at all but only a front facade of a house with nothing behind it. In this case, the perceptual expectations are frustrated and the perceiver is surprised. There is disagreement as to whether these pre-predicative aspects of regular perception should be understood as a form of cognitive phenomenology involving thinking. This issue is also important for understanding the relation between thought and language. The reason for this is that the pre-predicative expectations do not depend on language, which is sometimes taken as an example for non-linguistic thought. Various theorists have argued that pre-predicative experience is more basic or fundamental since predicative experience is in some sense built on top of it and therefore depends on it. Another way how phenomenologists have tried to distinguish the experience of thinking from other types of experiences is in relation to empty intentions in contrast to intuitive intentions. In this context, "intention" means that some kind of object is experienced. In intuitive intentions, the object is presented through sensory contents. Empty intentions, on the other hand, present their object in a more abstract manner without the help of sensory contents. So when perceiving a sunset, it is presented through sensory contents. The same sunset can also be presented non-intuitively when merely thinking about it without the help of sensory contents. In these cases, the same properties are ascribed to objects. The difference between these modes of presentation concerns not what properties are ascribed to the presented object but how the object is presented. Because of this commonality, it is possible for representations belonging to different modes to overlap or to diverge. For example, when searching one's glasses one may think to oneself that one left them on the kitchen table. This empty intention of the glasses lying on the kitchen table are then intuitively fulfilled when one sees them lying there upon arriving in the kitchen. This way, a perception can confirm or refute a thought depending on whether the empty intuitions are later fulfilled or not. Metaphysics The mind–body problem concerns the explanation of the relationship that exists between minds, or mental processes, and