 Nevertheless, we can assert that whatever sense of “conversion” seems compelling between mass and energy, it will have to be a “conversion” between mass and energy, and not between matter and energy. Finally, our observation obtains even in so-called “annihilation” reactions where the entire mass of the incoming particles seems to “disappear” (see, for example, Baierlein (2007, p. 323)). Of course, the older terminology of “matter” and “anti-matter” in the description of annihilation reactions does not really help our philosophical understanding of mass-energy equivalence and is perhaps partly to blame for some of the misconceptions surrounding \(E_o = mc^2\).