The theory of coherent systems has a foundation in the mathematics of binary logic. Whereas the results produced by this theory are mathematically elegant, their relevance to the behavior of actual systems is not so. Most systems cannot be classified as perfectly functioning or failed; in actuality, they often exist in degraded states.

In this talk, I will invoke the mathematics of multi-valued logic to produce a theory of vague coherent systems and produce results that parallel those of the binary theory. To do so, I use results from fuzzy sets and membership functions.