igation should be
_quasi ex contractu_ rather than _ex contractu_.

Our Anglo-American law of contracts was much influenced by this theory
of equivalents. In the seventeenth century four types of promise were
legally enforceable at common law: (1) A formal acknowledgment of
indebtedness by bond under seal, often conditioned upon performance of
a promise for which it was a security, (2) a covenant or undertaking
under seal, (3) the real contract of debt, and (4) a simple promise
upon consideration, that is, in exchange for an act or for another
promise. The first conclusively acknowledged an equivalent, in the
second it could be said that the seal presupposed or implied one, in
the third the obligation arose from the detention of something by him
to whom it had been delivered, and in the fourth the act or
counter-promise was the motive or consideration for the promise and as
a cause of or reason for making it was the equivalent for which the
promisor chose to assume the undertaking. With some aid from a
dogmatic fiction in the case of covenants, the common law could be
adjusted to this theory reasonably well. Accordingly as far back as
Bacon we find consideration treated from this standpoint in the
English books. But it was never a satisfactory explanation. If the
theory was sound it ought not to matter whether the equivalent was
rendered before the promise or after it or simultaneously with it.
Indeed, English equity in the nineteenth century took subsequent
action in reliance upon a promise of a gift to be a common-law
consideration on the basis whereof the promise was specifically
enforceable. Equity never wholly adopted this or any other theory. At
least after the middle of the eighteenth century equity was supposed
to follow the law as to what was a contract. But the common law was
not settled till the nineteenth century and we find the chancellors
using consideration frequently to mean not equivalent but any reason
for making the promise and thus making it synonymous with the
civilian's _causa_. The so-called meritorious consideration,
consideration of blood and of love and affection, and the cases of
promises sustained by moral obligation of a debtor to secure his
creditor, of a husband to settle property on his wife and of a parent
to provide for a child, show the idea of _causa_ at work in equity. It
is significant that Doctor and Student was often cited in these
connections. The most thoroughgoing attempt to a