The paper argues for viewing legal validity as a doxastic obligation, i.e.
as the obligation to accept a rule in legal reasoning. This notion of legal
validity is shown to be both sufficient for the laywers' needs and neutral
in regard to various theories of the grounds of validity, i.e. theories in
tended to identify what rules are legally valid, by proposing different gro
unds for attributing validity. All of these theories, rather then being alt
ernative definitions of validity, presuppose the notion here provided.
This notion is purely normative, but it allows for the construction of theo
ries of the grounds of validity which give due importance to social expecta
tions and institutions. As an example of how this may happen, one such theo
ry is also provided. This theory, which is presented through a detailed exa
mple of a judicial debate, is based upon the recognition of the (instrument
al) value of co-ordination, as the necessary way to achieve the most valuab
le purposes of the law.