  We discuss the variational principle within Quantum Mechanics in terms of the
noncommutative even Space Time sub-Algebra, the Clifford $\Ra$-algebra
$Cl_{1,3}^+$. A fundamental ingredient, in our multivectorial algebraic
formulation, is the adoption of a $\D $-complex geometry, $\D \equiv span_{\RR}
\{1,\gamma_{21} \}$, $\gamma_{21} \in Cl_{1,3}^+$. We derive the Lagrangian for
the Dirac-Hestenes equation and show that such Lagrangian must be mapped on $\D
\otimes {\cal F}$, where $\cal F$ denotes an $\Ra$-algebra of functions.
