The central dogma of molecular biology is a tenet of the field that holds in most cases. First described by Francis Crick in 1958, it states that RNA must be created by transcription from DNA, and further that protein can only be formed by translation from RNA. The conclusion is that DNA must somehow contain a complete set of instructions for the entire cell.
Like most biological "laws", the central dogma comes with its fair share of exceptions; for example, we know today that DNA can be reverse transcribed from RNA, and proteins can modify each other post-translation. The use of the word "dogma" was apparently a semantic error by Crick. He merely selected the wrong word, having no intention to introduce the connotation that the central dogma should be accepted as on par with unquestionable religious dicta.
