The classical theory of contract is based on the idea that rights and obligations arising out of a contract are fixed by the parties after taking into consideration all the pros and cons related thereto or flowing out of the same.. There are different kinds of agreements but the courts would recognise only those contracts which the parties seriously enter into and also with a view to create legal relationship. Those agreements which are mere "puff" or social agreements do not create any legal relationship (see Balfour v Balfour) and hence not enforceable in law. Thus only those agreements which are enforceable in law are recognised as contracts.
As I said earlier the parties are given the absolute freedom to contract. But this is an illusion. There are so many contracts where you really do not have any choice or freedom to fix terms. For eg Insurance contracts. There you have to sign on the dotted lines and if you do not agree with some of the terms then you either sign it or forget it. You will also find so many situations where you will be forced to agree though your mind is totally against the agreement. Then there are certain actions by the govt like levy sugar where you have to supply sugar to the govt whether you like it or not.
Under our contract Act it is stipulated that if consent is not freely given then the resultant agreement is voidable. Consent is said to be not freely given if the same is caused by coersion, undue influence, fraud, misrepresentation etc. There must be a distinction between situations where there is total lack of consent and where the Agreement is tainted with coersion etc. If you have not signed the agreement with an open mind but was forced to do so then you have a right to avoid such contracts.