Where this conjunction is of such a nature as to admit of division, but not of separation, the decision is natural and easy. The whole mass must be supposed to be common betwixt the proprietors of the several parts, and afterwards must be divided according to the proportions of these parts. But here I cannot forbear taking notice of a remarkable subtilty of the Roman law, in distinguishing betwixt confusion and commixtion. Confusion is an union of two bodies, such as different liquors, where the parts become entirely undistinguishable. Commixtion is the blending of two bodies, such as two bushels of corn, where the parts remain separate in an obvious and visible manner. As in the latter case the imagination discovers not so entire an union as in the former, but is able to trace and preserve a distinct idea of the property of each; this is the reason why the civil law, though it established an entire community in the case of confusion, and after that a proportional division, yet in the case of commixtion, supposes each of the proprietors to maintain a distinct right; however, necessity may at last force them to submit to the same division. Quod si frumentum Titii frumento tuo mistum fuerit: siquidem ex voluntate vestra, communc est: quia singula corpora, id est, singula grana, quæ a cujusque propria fuerunt, ex consensu vestro communicata sunt. Quod si casu id mistum fuerit, vel Titius id miscuerit sine tua voluntate, non videtur id communc esse; quia singula corpora in sua substantia durant. Sed nec magis istis casibus commune sit frumentum quam grex intelligitur esse communis, si pecora Titii tuis pecoribus mista fuerint. Sed si ab alterutro vestrum totum id frumentum retineatur, in rem quidem actio pro modo frumenti cujusque competit. Arbitrio autem judicis, ut ipse æstimet quale cujusque frumentum fuerit. Inst. Lib. II. Tit I. § 28.
Where the properties of two persons are united after such a manner as neither to admit of division nor separation, as when one builds a house on another's ground, in that case the whole must belong to one of the proprietors; and here I assert, that it naturally is conceived to belong to the proprietor of the most considerable part. For, however the compound object may have a relation to two different persons, and carry our view at once to both of them, yet, as the most considerable part principally engages our attention, and by the strict union draws the inferior along it; for this reason, the whole bears a relation to the proprietor of that part, and is regarded as his property. The only difficulty is, what we shall be pleased to call the most considerable part, and most attractive to the imagination.
This quality depends on several different circumstances which have little connexion with each other. One part of a compound object may become more considerable than another, either because it is more constant and durable; because it is of greater value; because it is more obvious and remarkable; because it is of greater extent; or because its existence is more separate and independent. 'Twill be easy to conceive, that, as these circumstances may be conjoined and opposed in all the different ways, and according to all the different degrees, which can be imagined, there will result many cases where the reasons on both sides are so equally balanced, that 'tis impossible for us to give any satisfactory decision. Here, then, is the proper business of municipal laws, to fix what the principles of human nature have left undetermined.
The superficies yields to the soil, says the civil law: the writing to the paper: the canvas to the picture. These decisions do not well agree together, and are a proof of the contrariety of those principles from which they are derived.
But of all the questions of this kind, the most curious is that which for so many ages divided the disciples of Proculus and Sabinus. Suppose a person should make a cup from the metal of another, or a ship from his wood, and suppose the proprietor of the metal or wood should demand his goods, the question is, whether he acquires a title to the cup or ship. Sabinus maintained the affirmative, and asserted, that the substance or matter is the foundation of all the qualities; that it is incorruptible and immortal, and therefore superior to the form, which is casual and dependent. On the other hand, Proculus observed, that the form is the most obvious and remarkable part, and that from it bodies are denominated of this or that particular species. To which he might have added, that the matter or substance is in most bodies so fluctuating and uncertain, that 'tis utterly impossible to trace it in all its changes. For my part, I know not from what principles such a controversy can be certainly determined. I shall therefore content myself with observing, that the decision of Trebonian seems to me pretty ingenious; that the cup belongs to the proprietor of the metal, because it can be brought back to its first form: but that the ship belongs to the author of its form, for a contrary reason. But, however ingenious this reason may seem, it plainly depends upon the fancy, which, by the possibility of such a reduction, finds a closer connexion and relation betwixt a cup and the proprietor of its metal, than betwixt a ship and the proprietor of its wood, where the substance is more fixed and unalterable.
[6] In examining the different titles to authority in government, we shall meet with many reasons to convince us that the right of succession depends, in a great measure, on the imagination. Meanwhile I shall rest contented with observing one example, which belongs to the present subject. Suppose that a person die without children, and that a dispute arises among his relations concerning his inheritance; 'tis evident, that if his riches be derived partly from his father, partly from his mother, the most natural way of determining such a dispute is, to divide his possessions, and assign each part to the family from whence it is derived. Now, as the person is supposed to have been once the full and entire proprietor of those goods, I ask, what is it makes us find a certain equity and natural reason in this partition, except it be the imagination? His affection to these families does not depend upon his possessions; for which reason his consent can never be presumed precisely for such a partition. And as to the public interest, it seems not to be in the least concerned on the one side or the other.