III. Thinking in the Service of Understanding the World

The feeling of possessing such a firm point caused the founder of modern philosophy, Renatus Cartesius,[^3] to base the whole of human knowledge on the principle, I think, therefore I am. All other things, all other events are present independent of me. Whether they are there as truth or illusion or dream I know not. Only one thing do I know with absolute certainty, for I myself bring it to its sure existence: my thinking. Perhaps it also has some other origin as well, perhaps it comes from God or from elsewhere, but that it is present in the sense that I myself bring it forth, of that I am certain. Cartesius had, to begin with, no justification for giving his statement any other meaning. He could maintain only that within the whole world content it is in my thinking that I grasp myself within that activity which is most essentially my own. What is meant by the attached therefore I am, has been much debated. It can have a meaning in one sense only. The simplest assertion I can make about something is that it is, that it exists. How this existence can be further defined I cannot say straight away about anything that comes to meet me. Each thing must first be studied in its relation to others before it can be determined in what sense it can be said to exist. An event that comes to meet me may be a set of perceptions, but it could also be a dream, a hallucination, and so forth. In short, I am unable to say in what sense it exists. I cannot gather this from the event in itself, but I shall learn it when I consider the event in its relation to other things. From this, however, I can, again, learn no more than how it is related to these other things. My search only reaches solid ground if I find an object which exists in a sense which I can derive from the object itself. As thinker I am such an object, for I give my existence the definite, self-dependent content of the activity of thinking. Having reached this, I can go on from here and ask: Do the other objects exist in the same or in some other sense?