The statement encapsulates a fundamental principle of contract law known as the 'mirror image rule' of acceptance. For a valid contract to be formed, there must be a clear and unequivocal agreement between the parties on all material terms. This principle is enshrined in the Indian Contract Act, 1872 (ICA), particularly in Section 7.

Section 7 of the Indian Contract Act, 1872: Section 7 states that "In order to convert a proposal into a promise, the acceptance must be absolute and unqualified." This means that the acceptance must correspond exactly with the terms of the offer. Any deviation, modification, or addition to the terms of the offer, no matter how minor, prevents the formation of a contract based on the original offer.

Vitiation of Acceptance by Departure or Qualification: When an offeree responds to an offer by introducing new terms, altering existing terms, or attaching conditions, their response is not a true acceptance. Instead, it is considered a 'counter-offer.'

1. Counter-Offer: A counter-offer has two significant effects:

   • Rejection of Original Offer: It automatically rejects and terminates the original offer. The original offer can no longer be accepted by the offeree.
   • New Offer: The counter-offer itself becomes a new offer, originating from the original offeree (now the new offeror) to the original offeror (now the new offeree). The roles of the parties are reversed.

   Example: If A offers to sell a car to B for ₹5 lakhs, and B replies, "I accept, but only if you include new tires," B has made a counter-offer. The original offer to sell the car for ₹5 lakhs without new tires is now terminated. A is free to accept or reject B's counter-offer.

2. Conditional Acceptance: An acceptance that is made subject to certain conditions or qualifications is not an absolute and unqualified acceptance. It is effectively a counter-offer. For instance, if an offeree states, "I accept, subject to contract," it implies that a formal contract is yet to be drawn up and agreed upon, and no binding agreement exists until then.

"Unless it is agreed to by the offeror": This crucial phrase in the statement provides the only way a contract can still be formed despite a departure or qualification in the acceptance. If the original offeror (who is now the offeree of the counter-offer) agrees to the modified terms, then a valid contract is formed based on those new terms. This agreement by the original offeror can be:

1. Express: The original offeror explicitly states their acceptance of the counter-offer. Following the example above, if A replies to B, "Okay, I will include new tires," then a contract is formed on the terms of B's counter-offer.
2. Implied by Conduct: The original offeror's actions or conduct may indicate their acceptance of the modified terms. For example, if A, after B's counter-offer, proceeds to install new tires and delivers the car, A's conduct implies acceptance of B's modified terms.

Established Principles:

• Consensus ad Idem: The mirror image rule ensures 'consensus ad idem' – a meeting of minds on the exact same terms. Without this, there is no true agreement.
• Certainty of Terms: It promotes certainty in contractual relationships, as parties know precisely what they are agreeing to.
• Communication of Acceptance: Acceptance must be communicated to the offeror. A mere mental assent is not sufficient.
• Lapse of Offer: An offer can lapse due to a counter-offer, rejection, revocation, or efflux of time. Once an offer lapses, it cannot be subsequently accepted.

Conclusion: In summary, the principle that acceptance must be absolute and unqualified is a cornerstone of contract formation under the Indian Contract Act, 1872. Any deviation from the original offer transforms the purported acceptance into a counter-offer, thereby terminating the original offer. A binding contract can only arise from such a situation if the original offeror subsequently agrees to the terms of the counter-offer, either expressly or by implication. This strict adherence to the mirror image rule ensures clarity, certainty, and genuine mutual assent in contractual agreements.