Article 1431 of the Civil Code defines estoppel as follows:
Art. 1431. Through estoppel an admission or representation is rendered conclusive upon the person making it, and cannot be denied or disproved as against the person relying thereon.
Meanwhile, Section 2(a), Rule 131 of the Rules of Court provides:
SEC. 2. Conclusive presumptions. – The following are instances of conclusive presumptions:
(a) Whenever a party has, by his own declaration, act, or omission, intentionally and deliberately led another to believe a particular thing is true, and to act upon such belief, he cannot, in any litigation arising out of such declaration, act or omission, be permitted to falsify it.
In estoppel, a party creating an appearance of fact, which is false, is bound by that appearance as against another person who acted in good faith on it.26 Estoppel is based on public policy, fair dealing, good faith and justice.27 Its purpose is to forbid one to speak against his own act, representations, or commitments to the injury of one who reasonably relied thereon.28 It springs from equity, and is designed to aid the law in the administration of justice where without its aid injustice might result.29
In Santiago Syjuco, Inc. v. Castro,30 the Court stated that “estoppel may arise from silence as well as from words.” ‘Estoppel by silence’ arises where a person, who by force of circumstances is obliged to another to speak, refrains from doing so and thereby induces the other to believe in the existence of a state of facts in reliance on which he acts to his prejudice.31 Silence may support an estoppel whether the failure to speak is intentional or negligent.32