pected effects have been discovered independently by different workers, but the ideal of repeatability has still to be achieved. Even with the best subjects on the top of their form, the psi effects are very weak. Also, another point importantly though differently related to these, the concept of psi is essentially statistical. Taken together these three facts mean that the testing of hypotheses, whether by reference to already recorded results or in new experiments, tends at present to yield imprecise or conflicting answers. If indeed the only laws we shall be able to formulate here are going to be statistical, it may be that the quantity of work needed to begin to establish them will be far greater than elsewhere. So until the present situation is radically changed -- either by important discoveries about the favouring and inhibiting conditions of psi, or by finding a way to distinguish between paranormal successes and chance hits singly, or by the sheer accumulation of experimental data -- the theoretical prospect seems likely to remain poor.