It is far better to foresee even without certainty than not to foresee at all.
Science is built up of facts, as a house is with stones. But a collection of facts is no more a science than a heap of stones is a house.
Science is facts; just as houses are made of stones, so is science made of facts; but a pile of stones is not a house and a collection of facts is not necessarily science.
Life is good for only two things, discovering mathematics and teaching mathematics.