  We investigate the relevance of the instanton-induced determinantal 't Hooft
interaction to the eta-nucleon coupling within the framework of a three-flavor
linear sigma model in the OZI-rule-respecting basis. Instantons, in combination
with the spontaneous breaking of chiral symmetry, are shown to provide the
major mechanism for the ideal mixing between pseudoscalar strange and
non-strange quarkonia. As long as 't Hooft's interaction captures most of the
basic features of the axial QCD gluon anomaly, we identify the anomaly as the
main culprit for the appearance of octet flavor symmetry in the anomalous
sectors of the pseudoscalar (and axial vector) mesons. Within this context,
unitary spin is shown to be an accidental symmetry due to anomalous gluon
dynamics rather than a fundamental symmetry in its own right. Though we find
the eta-nucleon coupling constant to obey a Goldberger-Treiman like relation,
the latter does not take its origin from a pole dominance of the induced
pseudoscalar form factor of the octet axial current, but from a subtle
flavor-mixing mechanism that is traced back to instanton dynamics. The model
presented allows for possible generalizations to non-ideal mixing angles and
different values of the meson decay constants in the strange and non-strange
sectors, respectively. Finally, we discuss the issue as to what extent the eta
meson may be considered as a Goldstone boson under the constraints of the
anomaly-produced unitary spin.
