Does an unreasonably held belief amount to fraud?

Lord Herschell makes it clear that while an unreasonably held belief is evidence of fraud, on its own it does not amount to fraud at 369: I think there is here some confusion between that which is evidence of fraud, and that which constitutes it. A consideration of the grounds of belief is no doubt an important aid in ascertaining whether the belief was really entertained. A man's mere assertion that he believed the statement he made to be true is not accepted as conclusive proof that he did so. There may be such an absence of reasonable ground for his belief as, in spite of his assertion, to carry conviction to the mind that he had not really the belief which he alleges. If the learned Lord intended to go further, as apparently he did, and to say that though the belief was really entertained, yet if there were no reasonable grounds for it, the person making the statement was guilty of fraud in the same way as if he had known what he stated to be false, I say, with all respect, that the previous authorities afford no warrant for the view that an action of deceit would lie under such circumstances. A man who forms his belief carelessly, or is unreasonably credulous, may be blameworthy when he makes a representation on which another is to act, but he is not, in my opinion, fraudulent in the sense in which that word was used in all the cases from Pasley v. Freeman down to that with which I am now dealing. ...