“The doctrine of marshalling applies where there are two creditors of the same debtor, each owed a different debt, one creditor (A) having two or more securities for the debt due to him and the other (B) having only one. B has the right to have the two securities marshalled so that both he and A are paid so far as possible. Thus if a debtor has two estates (Blackacre and Whiteacre) and mortgages both to A and afterwards mortgages Whiteacre only to B, B can have the two mortgages marshalled so that Blackacre can be made available to him if A chooses to enforce his security against Whiteacre. For the doctrine to apply there must be two debts owed by the same debtor to two different creditors.”
“two estates [were] mortgaged to A; and one of them mortgaged to B. He has no claim under the deed upon the other estate. It may be so constructed that he could not affect that estate after the death of the mortgagor. But it is the ordinary case to say a person having two funds shall not by his election disappoint the party having only one fund; and equity, to satisfy both, will throw him, who has two funds, upon that, which can be affected by him only; to the intent that the only fund, to which the other has access, may remain clear to him.”
“The reason is obvious ... [By] compelling [the first creditor with the two securities] to take satisfaction out of one of the funds no injustice is done to him ... . But it is the only way by which [the second creditor with one security] can receive payment. And natural justice requires, that one man should not be permitted from wantonness, or caprice, or rashness, to do an injury to another. In short we may here apply the common civil maxim: ‘Sic utero tuo ut non alienum laedas’; and still more emphatically, the Christian maxim, ‘Do unto others as you would they should do unto you’.”
“That doctrine is that when a prior creditor has one way of working out his preference which is less injurious to the postponed creditor than another, the prior creditor is bound either to adopt that course, or by assignation to put the postponed creditor into his right.”
“In the ordinary case of a catholic creditor – ie, a creditor holding security over two subjects, which for the sake of simplicity I shall suppose to be heritable subjects – and another creditor holding a postponed security over one of them, there can be no doubt that the catholic creditor is entitled to operate payment out of the two subjects as he best can for his own interest, but he is not entitled arbitrarily or nimiously to proceed in such a manner as to injure the secondary creditor without benefiting himself – as, for instance, capriciously to take his payment entirely out of the subjects over which there is a second security, and thereby to exhaust that subject, to the detriment of the second creditor, leaving the other subject of his own security unaffected or unexhausted. The second creditor will be protected against a proceeding so contrary to equity, and the primary creditor will be compelled either to take his payment in the first instance out of that one of the subjects in which no other creditor holds a special interest, or to assign his right to the second creditor, from whom he has wrested the only subject of his security.”
“The interest – ie the legitimate interest – of the primary creditor goes no farther than to get payment of his debt, and that is secured to him. The interest of the secondary creditor is to realize the value of his postponed security, and that is secured to him, in so far as is compatible with payment of the prior debt due to the primary creditor. The interest of the common debtor is truly nothing, or rather it is, or at least it ought to be, to allow both his creditors to receive full payment out of the subjects he had pledged to them.”