Assault, as it has been judicially defined, finds its basis in the protection against the apprehension of receiving harmful or offensive contact. It is the threshold for the more serious tort of battery, the actual contact with the person of the plaintiff. The law of assault has been developing over hundreds of years and will continue to do so. Of key importance to the tort, and the one factor more than any other which differentiates the tort of assault from other forms of intentional wrongdoing, is the element of apprehension in the mind of the victim. Without the awareness by the victim of the offered but uncompleted harmful or offensive contact, there is no basis for a cause of action sounding in assault. It is the mental tranquillity of the victim that the law of assault protects.
William H. Erickson, What Constitutes an Assault, 16 Clev.-Marshall L. Rev. 14 (1967)