Theology is the science of God. In order to understand this definition of theology, we must understand what a science is and its relation to philosophy and religion.

Theology may be defined as that human intellectual activity that investigates that part or aspect of reality that is believed to be ultimate reality and its relation to the rest of reality in order to acquire a body of general and systematic knowledge concerning it.

1. Theology and the Sciences.
   According to the definition of a science given above ( I.A), theology may be called a science. (There may be more than one theological science. If there are more than one, together they would form the theological sciences.) Theology is a science because it has the characteristics of a science: it is the investigation of some area or aspect of reality by the scientific method in order to acquire a body of general and systematic knowledge concerning it.
2. Theology and Religion.
   The area of reality that theology investigates is ultimate reality. But as pointed above ( V.A.3), the object of ultimate significance and supreme importance of a religion is believed to be ultimate reality. Since there are many different objects that are believed to be ultimate reality by different religions, there will be many different theologies (Christian, Buddist, Mohammedan, etc. theologies). Thus there will be many theologies as there are many different objects that are believed to be ultimate reality. Accordingly there will be as many intellectual constructions called theologies, even though there is only one theology as an intellectual activity. Now it is obvious that theology as an intellectual activity should be and is carried on from within and presupposes an ultimate commitment. Thus theology and religion are closely related to each other.
3. Theology and Philosophy.
   Insofar as theology is carried on from within and presupposes an ultimate commitment, theology is similar to philosophy. But theology differs from philosophy in that it is primarily concerned with ultimate reality and not with those aspects of reality characteristic of it as a whole. Theology is interested in these latter aspects only because the nature of ultimate reality involves them. Thus it is that theology needs philosophy. On the other hand, philosophy must depend upon theology for its knowledge of ultimate reality. Although theology and philosophy are thus interrelated, they are different; they differ formally from each other in the same way that philosophy differs from the sciences as a whole (see III.B above). But theology is related to philosophy similarly as philosophy is related to the other sciences (see III.C above).