Fun with Pleading in the Alternative

From Fowler v. Bott, 6 Mass. 63 (1809):

[I]t appears that the plaintiffs thereby covenanted, among other things, to build a chocolate mill, in a place agreed upon, of certain dimensions, and in a certain manner mentioned in the indenture: and did, in and by the same indenture, “grant, lease and demise the same chocolate mill, with the privileges and appurtenances thereto belonging,” to the defendants for the term of six years…

The defendants pleaded three several pleas in bar.

1. That the plaintiffs never built a chocolate mill in the place, &c. according to the form and effect of the said indenture. …

3. That after the commencement of the lease, and before any of the rent for which this action is brought accrued or was in arrear, the said chocolate mill was, against the will and without the default of the defendants, burned and consumed by fire … .