  The geometric calculus based on Clifford algebra is a very useful tool for
geometry and physics. It describes a geometric structure which is much richer
than the ordinary geometry of spacetime. A Clifford manifold ($C$-space)
consists not only of points, but also of 1-loops, 2-loops, etc.. They are
associated with multivectors which are the wedge product of the basis vectors,
the generators of Clifford algebra. We assume that $C$-space is the true space
in which physics takes place and that physical quantities are Clifford algebra
valued objects, namely, superpositions of multivectors, called Clifford
aggregates or polyvectors. We explore some very promising features of physics
in Clifford space, in particular those related to a consistent construction of
string theory and quantum field theory.
