  We compute the axial, scalar, tensor and pseudoscalar isovector couplings of
the nucleon as well as the induced tensor and pseudoscalar charges in lattice
simulations with $N_f=2$ mass-degenerate non-perturbatively improved
Wilson-Sheikholeslami-Wohlert fermions. The simulations are carried out down to
a pion mass of 150 MeV and linear spatial lattice extents of up to 4.6 fm at
three different lattice spacings ranging from approximately 0.08 fm to 0.06 fm.
Possible excited state contamination is carefully investigated and finite
volume effects are studied. The couplings, determined at these lattice
spacings, are extrapolated to the physical pion mass. In this limit we find
agreement with experimental results, where these exist, with the exception of
the magnetic moment. A proper continuum limit could not be performed, due to
our limited range of lattice constants, but no significant lattice spacing
dependence is detected. Upper limits on discretization effects are estimated
and these dominate the error budget.
