In this text, I propose a particular analytical view on SIMD architectures. Identifying five distinct classes of capabilities of SIMD instruction set architectures then allows me to assess the general power and applicability of any specific SIMD ISA, without the need to resort to some hopefully representative sample of algorithms. I will illustrate this idea with a coarse analysis and comparison of past and future SIMD architectures. Ultimately, we will gain a deeper understanding of the weaknesses of vector processors, and how to fix them.