upon a past event unknown to the parties. Is this statement valid? my wife. Negative impossible conditions are deemed not written, as such it is considered as a pure obligation unless there are other words and This is not valid. To be pure it must not be phrases which would not make it a pure obligation. conditional and not with a term. In the above statement both the future and uncertain must both concur and this would only exclude a condition. A term can never be uncertain. It is just a space of time. An event is certain to happen. Therefore it should be or. If "and" is used, it would only exclude a condition with a condition and not those with a term. If or is used it would exclude obligations with a conditions and also those with a term. Yes. If the condition though impossible is in the