  In this article we give a construction of a polynomial 2-monad from an operad
and describe the algebras of the 2-monads which then arise. This construction
is different from the standard construction of a monad from an operad in that
the algebras of our associated 2-monad are the categorified algebras of the
original operad. Moreover it enables us to characterise operads as categorical
polynomial monads in a canonical way. This point of view reveals categorical
polynomial monads as a unifying environment for operads, Cat-operads and clubs.
We recover the standard construction of a monad from an operad in a
2-categorical way from our associated 2-monad as a coidentifier of 2-monads,
and understand the algebras of both as weak morphisms of operads into a
Cat-operad of categories. Algebras of operads within general symmetric monoidal
categories arise from our new associated 2-monad in a canonical way. When the
operad is sigma-free, we establish a Quillen equivalence, with respect to the
model structures on algebras of 2-monads found by Lack, between the strict
algebras of our associated 2-monad, and those of the standard one.
