The fact the plaintiff was bound to prove, in order to obtain further relief than that which was granted to him, was, that the Gamble judgment formed part of the consideration of the mortgage debt. The fact, if it exists, must be within the knowledge of the parties, and, so far as appears, in reference to it there ought not to be cause or room for dispute. Their evidence is, however, in that painful and irreconcilable conflict which too often characterizes the testimony of litigating parties, embarrassing rather than aiding the administration of justice. As we have said, the burden of proving the fact rests upon the plaintiff ; it is an affirmative fact pleaded by him as the basis of the relief prayed. The fact being denied and put in issue, if the evidence of it is equally balanced, or if the evidence does not produce a just, rational belief of the existence of the fact, if it leaves the mind in a state of doubt and uncertainty, the party affirming the fact fails for want of proof.—Lehman v. McQueen, 65 Ala. 570. We have carefully examined the testimony, and we fail to discover that the chancellor erred in the conclusion that the fact was not satisfactorily proved ; and the decree must be affirmed.