Ever since the introduction of NOS into the new syllabus I have been trying to figure out what the difference is between NOS and TOK. For years I have been literally ringing the TOK bell in my physics class, that means that if I (or one of my students) ever mentions something that might be interesting to talk about in a TOK class a bell is rung. Every lesson has ringable moments, from the way we use Laws, or models to evaluating results and quoting uncertainties. All of these examples would now be termed NOS but that doesn't mean that they are no longer TOK. In a recent workshop I asked a representative from the IB what the official difference was. The answer is that NOS will be examined TOK won't. I've just been working on a page giving examples of each different aspect of NOS and I've come up with an alternative definition. NOS questions can be answered TOK questions don't necessarily have an answer. That's why you can't ask an exam question on TOK. The actual formulation of NOS questions is still a bit of a mystery, will there be questions asking for examples of NOS like "give an example of a Law in Physics" or will they be asking students to use NOS in which case many existing questions could be termed NOS for example, "how did the results of Rutherfords experiment show that the plum pudding model wasn't correct?"