Rene Descartes once said: Cogito Ergo Sum (including capitals), meaning I think, so I am in current english. Or in the language of the man in the street: Methinks Iam.
Lets investigate why the statement I think, so I am (I quit with the latin) is a non-statement.
Applying the statement to more people
In Descartes' time people usually expressed their ideas in latin, for then they had to learn only one foreign language to get everybody that was somebody to be able to understand them. Latin was used because for many centuries it had been the common european language for religion and science, nobody would have it as a national language, and so no country could feel more equal than other countries by using it.
Descartes obviously knew that there were more people, and that some of them were capable of thinking also, otherwise he wouldn't have bothered using latin at all. So he wrote his statement to them.
His friends may have thought: He may be, but so do I and so I am.
After that line of thought they wrote back You think, so you are and as the message had been cc'd they came also with: He thinks, so he is, and the multiple combinations with we, you and them.
We have now a number of people thinking they are because they are thinking. Put into the by now familiar formula: Some people think, so they are.
Applying the statement to all people
Is it also possible to extrapolate this to all people, can we say: All people think, so all people are?
Obviously not, as every army recruit keeps hearing from his sergeant that he doesn't think, and 'a thinking politician' is a contradictio in terminis (Sorry, but this looks better in latin).
This results in Some people do not think, but they are.
Combining this, we are left with: Whether or not they think, people are. Using the rules of logic we can skip the first part, so this reduces to simply People are, which contains no usefull information at all, since this was known from the beginning.
Execpt for Descartes of course, he didn't know he was until he thought he started thinking.
Applying the statement to non people
Can we expand the system to outside the human race, for instance with cats, dogs, horses, trees or stones?
Have a good look at a cat, and it certainly thinks, mostly about how to trick you into giving it more and better food.
In the days of Descartes there was also doubt about the status of women and non-white races as humans, although they certainly were, and some of them sometimes even seemed to think. Of course we now know better, they are and they do think.
So now we have also whether or not it thinks, it is, which can be reduced to It is, again a non-statement containing no information at all.
Combining all this we can say that Descartes' statement is just a special case of saying nothing at all.
Earlier more successful tries
The opposite of Descartes' statement is also investigated far in the past by early types of human as Cro Magnon, when they invented thinking. For them the statement was I am, so I think. This they did in their own language, as latin had not yet been invented.
Expanding it first to other people and after that to animals, stones, weather and stars, they recognised that much of their misfortunes or fortunes coincided with actions on the part of those categories.
This implied of course thinking so they ended up with Everything is, so everything thinks.
Politicians or sergeants had not been invented yet, so there didn't have to be exceptions.
Thinking about the consequences of this rule, they had no alternative than inventing religions, where all objects and animals were supposed to think and to be able to influence human life. To make life less dangerous than it allready was, all animals, trees, the weather and so on, had to be kept friendly.
The best thing about their friendlines you then could hope for was: I think they are.