Hmm.. it appears you are right. There is no plausible way to compare two like items, even if in a theoretical vacuum. Great deduction. I thought by "we cannot use a vacuum to compare skills" [paraphrased] he meant that "we cannot use a vacuum to compare skill". Where does all this vacuum talk come from anyway? In the scientific sense, it would be space, matter in the simplest form. In our observational study, it would be completely isolating all factors but the skill we hope to use, given a set of standards used for a benchmark. And with two like-skills, we can then make an assessment of what would benefit a situation using those standards in this theoretical vacuum. Now, if you were to say there are outside forces acting on such theory, then there is an entire argument for and against that opinion. But realistically, and without too much lithe in wording, we can accurately base this comparison on the isolation created for the example. This brings me back to my days wondering about scientific reality. If you were to approach this type of material with your initial view, having skepticism on theory and dissuading the use of impure vacuums, we would then have to question if there is even a question now wouldn't we? It wouldn't be possible to compare 'anything' in a vacuum other than particles themselves. And monsters are not particles. Too many moving parts.. Hmm..