When they are generic, non-count nouns and sometimes plural count-nouns are used without articles. "We like wine with our dinner. We adore Baroque music . We use roses for many purposes." But if an "of phrase" comes after the noun, we use an article: "We adore the music of the Baroque." Also, when a generic noun is used without an article and then referred to in a subsequent reference, it will have become specific and will require a definite article: "The Data Center installed computers in the Learning Center this summer. The computers, unfortunately, don't work."