Evolution: a belief or a fact?

It is not uncommon to "meet" people on the net who are critical of others who "believe" in evolution. I think the term "believe" is not the correct one here. Is evolution scientifically proven? Probably not in the sense in which e.g. the theory of gravitation is. It does however make a lot of sense, and as far as I can judge, it is consistent with what can be observed of nature.

I too was once suspicious about evolution. It is hard to believe that we evolved from a bunch of cells swimming in sea water.

I changed my mind after considering what is required for evolution to work. Each of these prerequisites is in itself so simple and obvious that no sensible person can reject it. So what is needed for evolution to take place?

First, you need a genetic code that decides survival. This genetic code need not be the only factor deciding survival, but it should be relevant.

Then, you need heredity. Parents must be capable of passing their genes to their children.

If the reproduction mode is cloning, i.e. one parent alone is capable of generating children, as is the case for viruses, then mutations are needed to introduce new features.

These ingredients are all that is needed for evolution to work. Because I do not doubt any of these ingredients, I am left with no other option than to "believe" in evolution. I am quoting the word "believe", because my acceptation of the theory of evolution is not based on faith, but on rational thinking.