Coke defines Estoppel, as existing, when "a man's owne act or acceptance, stoppith or closeth up his mouth to alleage or plead the truth." (a) This definition is accepted by Comyn. (b) But while it seems to justify a part at least of the opprobrium which has been cast upon estoppels, it does not appear to prevent a just view of them. We should say rather, that an estoppel was an admission or a declaration, which the law does not permit him who has made it to deny or disprove for his own benefit, and to the injury of another.

Estoppel may be used as a defence against a party who is thus precluded by his act or statement from maintaining his action; or it may be used by a plaintiff to prevent or avoid a defence which is open to a similar objection.

The law of estoppels, especially in reference to deeds and real • actions, had become so much embarrassed and ob • 788 scured by technicalities, and was so often used as a means of injustice, that it became a common saying, that "estoppels are odious in the law." (c) But as they are now regulated and practised, we should say that there was but little ground for, and but little force in, this principle.

(a) Co. Lift. 352 a. "Touching estoppels, which is an ancient and curious kind of learning," Coke, in the passage cited, gives these among other rules: That every estoppel ought to be reciprocal, that is, to bind both parties, and this is the reason that regularly a stranger shall neither take advantage nor be bound by an estoppel, but all strangers shall take benefit of that record which doth run to the disability of a person. And see Doe v. Errington, 6 Bine. N. C. 79; Lansing v. Montgomery, 2 Johns. 382; Worcester v. Green, 2 Pick. 425; Langer v. Felton, 1 Rawle, 141; Wright v. Hazen, 24 Vt. 143. It must be certain to every intent, and not be taken by argument nor inference; matter alleged that is neither traversable nor material does not estop; an estoppel against an estoppel puts the matter at large. Carpenter v. Thompson, 3 N. H. 204. Where verity is apparent in the same record, there the adverse party shall not be estopped to take advantage of the truth. Sinclair v. Jackson, 8 Cowen, 543.

(b) Com. Dig. Estoppel, A. 1 Comyn, same title, E. 1 to 10, in addition to Coke's recapitulation, says, there is no estoppel by a record coram non judice, nor by an unauthorized act in pais, nor if an interest passes from a party; i. e. though lessor's title at time of demise may not be disputed, its expiration may be shown. Doe v. Seaton, 2 Cromp. M. & R. 728; Neave v. Moos, 1 Bing. 360, 8 J. B. Moore, 389.

(c) Lampon v. Corke, 5 B. & Ald. 606; Owen v. Bartholomew, 9 Pick. 520; Steinhauer v. Witman, 1 S. & R. 438.

They are of many kinds; which may be arranged in three classes: 1. Estoppels by Record; 2. Estoppels by Deed; 3. Estoppels in Pais.