1. Use of spice and spices and pizza and pizzas under context:

In everyday situations, I think hearing or seeing no. 1 wouldn't be awkward to see or hear, whereas no.2 would be to the contrary, because it is assumed that a normal household would have a various kinds of spices to spice up ther cooking. But no. 2 would be awkward at best considering the use of the word 'pizzas' in everyday sitations because we don't usually have different-sized pizzas or kinds of pizzas at home at one time and it is inconceivable to encounter slicing them when they are packed high one after the other. But it seems odd that one is possibly good and the other is not.

1. Grind spices into a fine powder.
2. Cut pizzas into thick, small slices that are piled rather high.

2. I think the use of 'injustices' is preferred, if not correct.

Use of the words Injustice and Injustices:

John sees children in third-world countries not getthing proper education and living in poverty and to that, he voices that the injustices of world poverty must be put under control for the sake of humanity.

3. If you have some idea of what my area of difficulty is, would you tell me what might help me? I think a general or instance (or example) version use of a variable noun is correct as long as the context and the intent of the writer is are in line with the general model of its usage recommendation, which seems to be that use the uncountable version when referring to it abstractively and use the countable version when referring to its individual example (or examples) or instance (or instances). Having said it, I find the pragmatic use of a variable noun difficult. Do you have some tips?
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Thank you. Let me cut to the chase (if that is a proper expression to use) and go to the meat of the matter: When you are using a variable noun like "injustice" and "discussion," I think you can refer to something generally or refer to something as its examples or instances. I don't have a lot of problems with the aspect of using the kind of it to refer something in an abstract fashion. It is the countable use that troubles me: What are some factors that influence its usage? Are these some of them?

1) perpective of the writer -- whether he or she is perceiving the use situation as examples or in an abstract fashion,
2) contextual demand -- whether the context of text in consideration demands the use of a countable version

Would you say if one of two listed is present, then it is OK (correct) to use the countable version of a variable noun like "injustice" and "discussion"?

I think my question is rather vaguely phrased or the structure is not mapped out clearly.
I suppose we have dealt with this on your [url=http://www.EnglishForward.com/English/VariableNoun/gvgkm/post.htm ]OTHER THREAD[/url]?