  We consider multi-particle contributions to nucleon two- and three-point
functions from the perspective of chiral dynamics. Lattice nucleon
interpolating operators, which have definite chiral transformation properties,
can be mapped into chiral perturbation theory. Using the most common of such
operators, we determine pion-nucleon and pion-delta couplings to nucleon two-
and three-point correlation functions at leading order in the low-energy
expansion. The couplings of pions to nucleons and deltas in two-point functions
are consistent with simple phase-space considerations, in accordance with the
Lehmann spectral representation. An argument based on available phase space on
a torus is utilized to derive the scaling of multiple-pion couplings. While
multi-pion states are indeed suppressed, this suppression scales differently
with particle number compared to that in infinite volume. For nucleon
three-point correlation functions, we investigate the axial-vector current at
vanishing momentum transfer. The effect of pion-nucleon and pion-delta states
on the extraction of the nucleon axial charge is assessed. We show that
couplings to finite volume multi-particle states could potentially lead to
overestimation of the axial charge. Hence pion-nucleon excited states cannot
explain the trend seen in lattice QCD calculations of the nucleon axial charge.
