We to critique the following question: can we have reasonable certainty that the terms in speculative or empirical theories correspond meaningfully to things in the ontological structure of the world, or are they only convenient fictions useful for predicting phenomena? We first justify this question as meaningful, and capable of admitting a meaningful answer. We then analyze question itself with examples from physics and biology. We conclude that we can be reasonably certain that the terms in an empirical theory have (...) some degree of ontological significance, provided that they are directly related to phenomenal experiences. We also suggest that the advance of science can be aided through this understanding. Finally we use these conclusions to analyze the existence of the mind and certain physical structures. (shrink)