15 Recognition and enhancement of freedom in some respects

Within the essential limits just noted, the principle of party autonomy is reflected in Book VIII. It can be seen in the rule that the parties to a transfer of goods can generally determine by agreement the point in time when ownership passes,1. and in the rule that the consequences of the production of new goods out of another's goods or of the combination or commingling of goods belonging to different persons can be regulated by party agreement.2. The rules on proprietary security in Book IX can be seen as enhancing freedom (and efficiency) by opening up wide possibilities for the provision of non-possessory security, something which has not traditionally been possible in many legal systems. Similarly, the rules on trusts in Book X could enhance freedom by opening up possibilities for setting property aside for particular purposes (commercial, familial or charitable) in a flexible way which has been much used and much valued in some systems for a very long time and is gradually spreading to others.