Can I publish work without a Creative Commons licence? Why/why not? All I am doing is teaching general knowledge.

I'm replying to this old post only because it showed up high on my search concerning Creative Commons and it misconstrues the nature of Creative Commons. CC does not impose the same kind of restrictions implied by this question. There are subtypes of CC that require attribution be given to a creator when his/her material is used, or that forbid re-use that makes changes instead of merely quoting, or that forbids only re-use for commercial gain, but the simple full Creative Commons is a kind of anti-copyright that permits anyone to do anything with your work.