The court's point in the ensuing paragraph is worth emphasizing and expanding. Clearly, real property law and Article 9 permit the use of future advance clauses in security instruments. Their interpretation and enforceability, however, are subject to general common law principles of contract law, including principles of interpretation (including the parol evidence rule), unconscionability, fraud, duress, mistake, and others. In the context of personal property security, note UCC 1-103.