In our ontological discussion of reality we have distinguished the first domain of reality from the second and higher-order domains. We ourselves and all animals, plants and nonliving, concrete things belong to the first domain, whereas attributes and relations, and catenas of attributes and relations, belong to the second. We have now also distinguished three spheres of reality which do not concern existence per se but the nature of the relationship between existing things. This encompasses the relationship between a thing and an attribute which it has or does not have, which it can have or cannot have, and which it should have or should not have. In practise this triadic sphericity of reality only seems to make sense for the first domain of discourse, for this is the domain in which we as persons can exert our influence, and can be influenced ourselves by what should be.

The ontological system we have developed is a body of thought about existence, about reality. Until now it has been confined to those things (real or hypothetical) which were not thoughts or systems of thought themselves, and we have assumed that this reality is independent of the thoughts about it. Hence, when a person is (said to be) thinking about something, this thinking itself does not make it exist, nor does it cause it to have a certain part or determinative predicate -- at the most the thing may get a reflectional predicate as a result of this thinking (see 2.3.1). We vehemently reject the idea that all existence, and all facts, modes and norms, would be dependent of, that is, immediately occasioned by, thoughts or feelings about them (including sense perception). We even more vehemently reject the solipsist idea that all existence and the factual, modal or normative forms of reality would solely depend on 'my' mental processes, or the anthropocentrist idea that they would all depend on the mental processes of human beings exclusively. Thinking may affect the existence and shape of certain things very much, but only indirectly after subsequent action has been taken. It is, then, the action which affects it, not the thinking itself in a strict, direct sense.

From the perspective of the process of thinking reality consists of:

• one or more persons thinking about reality (having thoughts about what is, can or should be);
• thoughts (about reality as it is, can or should be);
• the reality thought about (the rest being the reality not thought about).

As we have, until now, included into our ontological framework only entities which are not thoughts themselves, we have not yet left the lowest level of a new ontological hierarchy: that of zero-, first- and higher-order levels of propositional reality. The zero-level is, then, the level of nonpropositional reality to which we belong ourselves as persons and as bodies. But also predicates and catenas belong to this level, and facts, modes and norms insofar as they pertain to relationships between nonpropositional entities.

The term proposition will be employed here as a synonym of (primary) truth-bearer, as something which is true or false. This accords quite well with the etymology of the word and (one of) its lexical meaning(s). It depends on which theory of truth or truth-bearers one adheres to, whether a proposition (in this sense) is the same as the meaning of a sentence, a sentence, a sentence token, an utterance, a statement, or something else of that ilk. The availability of the concept of proposition is far more important here than the question of its final formal analysis, tho its use might give the appearance of wholly committing ourselves ontologically. However, all the claims in which we make use of the concept of a proposition, or in which we differentiate the propositional and the nonpropositional, are indifferent between the options mentioned. Whether a proposition is something abstract, such as a thought or the meaning of a sentence, or something more concrete, such as a sentence token or an utterance, we can (and must) tell a nonpropositional reality apart from a propositional reality. And, furthermore, it is essential that such a proposition is always about something.

Propositional reality is the world of propositions or propositional attitudes. Attitudes are hypothetical constructs in which a person's diverse thoughts, feelings and tendencies to act are arranged into a more or less coherent pattern. The cognitive aspect of someone's attitude concerns 'er thoughts and beliefs; the affective aspect the feelings 'e has about something; and the conative, aspect the person's behavioral tendencies. The expression propositional attitudes, refers, first of all, to the thoughts and beliefs people have about reality as it is thought or believed to be. We shall not exclude the possibility that it also refers to people's feelings and behavioral tendencies if, and insofar as, they are expressed in or translatable into propositions or statements. Thus verbs of propositional attitude are not only verbs such as to know but also verbs such as to hope and to intend. Propositional reality is then also the world of feelings, intentions, conscious desires and tendencies about and with respect to reality as it is felt to be, intended to be, and so on. Thinking, however, is the phenomenon most typical of propositional reality, and we shall often only mention thoughts for the sake of simplicity.

In the first instance thoughts are thoughts about nonpropositional reality, but they may also become the object of thought themselves, and these thoughts about thought too may, again, become the object of thought, and so on and so forth. Hence, whereas there is merely one level of nonpropositional reality from the propositional point of view, namely the zero-level, there is in principle no definite number of levels of propositional reality. Thoughts about nonpropositional reality constitute first-order propositional reality, those about first-order propositional reality, second-order propositional reality, and so on. However, second-order propositional reality does not only encompass thoughts about (or propositional attitudes towards) thoughts about nonpropositional reality, it also encompasses thoughts about (and propositional attitudes towards) the special relationship between first-order thoughts and nonpropositional reality. And this relationship may be factual, modal or normative, like any relation within first-order propositional reality. The beginning of this hierarchy of propositional levels is shown in figure I.3.2.1.1. It is obvious that when speaking of "lower" and "higher levels" in this hierarchy, the words lower and higher must not be given the connotation of worse or inferior and better or superior. We could have labeled the zero-level "the highest level" and every next level "a lower level". As in any objective, theoretical hierarchy these words do not have any evaluative significance here.