Humans have attempted to disrupt the progression of pregnancy for a very long time. This dates back to the realization that it was a sexual activity which started the reproductive cycle. Folk methods for preventing pregnancy after unprotected sexual activity are physiologically unable to be effective and we now have chemical, mainly hormonal methods, and a mechanical method the intrauterine device which do work in the very early stages before conception can be diagnosed with certainty. These methods are impeded by those who worry that fertilisation of the ovum may have occurred, and that the method may then be abortifacient. Considering that it is possible to easily disrupt an established pregnancy by medical or surgical means depending on the duration, this would be no different than any other means of abortion induction. This evaluation takes the approach of viewing pregnancy as a 40 week continuum and that the approach to halting it after it has begun should simply be chemical or mechanical depending on duration and subject preference and clinical suitability as appropriate. There is no clinical reason to not be able to act in the early stages before the diagnosis of pregnancy is determinable. Clinicians may want to use the duality of conceived and non-conceived simultaneously if it helps to take action to interrupt the pregnancy continuum so that they may view their client as pregnant or is not pregnant enabling them to act accordingly. This could be viewed as the uncertainty principle of emergency contraception. The methods available and their historical context and limitations are presented and examined. Emergency Contraception: History, Methods, Mechanisms, Misconceptions and a Philosophical Evaluation; Norman D Goldstuck.