The Parol rule of evidence is a feature of the interpretation of the contract, since it is necessary to verify whether a document constitutes a partial or complete declaration of the parties` agreement.  In the common law world, this provision is adopted in a way that promotes safety and predictability when executing the contract.  This finding is intended to determine the importance of the language of the contract and thus excludes evidence of pre-contract negotiations used to interpret the treaty.  There is a discrepancy here between the common law and the theoretical civil approaches to contract formation and therefore construction. The Parol rule of evidence was described by Blackburn J. in Smith v Hughes.  He stated: „Whatever the real intention of a man to behave in such a way that a reasonable man would think that he would accept the terms proposed by the other party, and it is that party that concludes the contract on the basis of that conviction that the man would also be bound by the treaty as if he intended to approve his terms.“  Witnesses are also considered evidence. If you had someone present at the time of the verbal agreement, they may be subpoenaed to testify. All written communications regarding the agreement, including texts and emails, are also included. Finally, a letter that is not the treaty, but which is signed by the party who denies it, which admits that a contract has been concluded, can create a binding contract, even if the underlying treaty was verbal: the judgment in the Innoviva case is important because it says a lot about who we are as a society and it has a tangible impact on the profitability of the economy. Are we a society that believes in personal integrity and responsibility? Or are we a society where people don`t need to live up to what they say and give up their promises? The Innoviva case is a victory for a more decent and civilized society, where people are bound by their agreements.
If someone you`re dealing with promises you something, they have to do it, whether or not that promise is reduced to writing.