  Even if there is no objection in principle, there appears to be a conflict between interactionism and some basic principles of physical science. For example, if causal power was flowing in and out of the physical system, energy would not be conserved, and the conservation of energy is a fundamental scientific law. Various responses have been made to this. One suggestion is that it might be possible for mind to influence the distribution of energy, without altering its quantity. (See Averill and Keating 1981). Another response is to challenge the relevance of the conservation principle in this context. The conservation principle states that ‘in a causally isolated system the total amount of energy will remain constant’. Whereas ‘[t]he interactionist denies…that the human body is an isolated system’, so the principle is irrelevant (Larmer (1986), 282: this article presents a good brief survey of the options). This approach has been termed conditionality, namely the view that conservation is conditional on the physical system being closed, that is, that nothing non-physical is interacting or interfering with it, and, of course, the interactionist claims that this condition is, trivially, not met. That conditionality is the best line for the dualist to take, and that other approaches do not work, is defended in Pitts (2019) and Cucu and Pitts (2019). This, they claim, makes the plausibility of interactionism an empirical matter which only close investigation on the fine operation of the brain could hope to settle. Cucu, in a separate article (2018), claims to find critical neuronal events which do not have sufficient physical explanation.This claim clearly needs further investigation.