Insurance is a contract based upon speculation. The special facts, upon which the contingent chance is to be computed, lie most commonly in the knowledge of the insured only; the underwriter trusts to his representation and proceeds upon the confidence that he does not keep back any circumstance in his knowledge, to mislead the underwriter into a belief that the circumstance does not exist, and to induce him to estimate the risque as if it did not exist. Good faith forbids either party by concealing what he privately knows, to draw the other into a bargain from his ignorance of that fact, and his believing the contrary. This was an attempt by Mansfield to introduce the assumption of good faith into English law, and although it failed for the most part (as most areas of English commercial law no longer use "uberrima fides"), it is still used in insurance contracts. In insurance agreements, the insuree inevitably knows more about the risk involved than the insurer; without the requirement for pre-contractual "good faith," the insuree would have no reason to tell the truth, and insurance companies would be loath to make contracts.