 If intra-textual treatment does not clearly yield the intention of the parties, the interpreter must look to the extended context to draw useful inferences from the nature of the contract, its purpose and the background against which it was concluded.In other words, only if a consideration of the language in its contextual setting fails to produce sufficient certainty (the degree of certainty required being left to the discretion of the individual judge) may evidence of “surrounding circumstances” be led.Even then, however, recourse may not be had to evidence of what passed between the parties in the course of negotiating the contract unless a consideration of the “surrounding circumstances” fails to resolve the difficulty.