growth of fruit or the pregnancy of animals, or in an artificial way. The various methods may be classified as: Land to land by accretion or alluvion Moveables to land or fixtures Moveables to moveables Moveables added to by the art or industry of man Accession in relation to land The general principle was that everything acceded to the land, since the land was the principal. Buildings (inaedificatio) Ownership of the house was considered distinct from ownership of the materials used to make the house. Owners of the materials were permitted to vindicate the materials upon demolition of the house, but the demolition of the house was forbidden by the Twelve Tables. Where X built on X's land using Y's materials, X owned the house since it acceded to X's land. Y would be capable of laying one of two actions if X was in good faith (bonas fides) in using Y's materials, but two actions if X was in bad faith (mala fides). These actions were (i) the vindicatio for the materials and (ii) the actio de tigno, which would recoup twice the value of the materials. Additionally, Y would also have an action against a third party if that third party stole the materials. In A Text-Book of Roman Law from Augustus to Justinian, W. W. Buckland discusses a third situation where X builds on Y's land using Z's materials. In such a situation, Buckland suggests that in relation to Y, X should be treated as though an XYX situation has occurred, and in relation to Z, as though an XXZ situation has occurred. Plants and seeds X's plants and seeds acceded irreversibly to Y's soil once they have taken root, but Y must pay expenses if X is in legal possession, since X will have the exceptio dolus malus against Y's vindicatio. Rivers and new islands Alluvion Avulsion Accession in relation to movables The accessory accedes to the principal. The debate is generally over which is the principal and which is the accessory. The principal owner owns regardless of good faith, bad faith, or consent. Possible tests that could be adopted in deciding this question include: Economic value Size Physical identity Relative non-economic value in terms of aesthetic value or labor In Roman law, there was no consistency. Everything was decided on a casuistic basis. The Physical Identity test was the dominant test, i.e., the principal is