Contracts are promises that the law will enforce. Contract law is generally governed by the common law of the State and, while general contract law is common throughout the country, some specific judicial interpretations of a particular element of the treaty may vary between States. Each contracting party must be a “competent person” who is legitimate. The parties may be natural persons (“individuals”) or legal persons (“limited communities”). An agreement is reached when an “offer” is accepted. The parties must intend to be legally bound; and, to be valid, the agreement must have both an appropriate “form” and a legitimate purpose. In England (and in jurisdictions that apply English contractual principles), parties must also exchange “considerations” to create “reciprocity of engagement,” as in simpkins v Country.