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Narrow-line Seyfert 1 galaxies are defined on the basis of their line widths,and they are generally considered to be high Eddington ratio sources. But inthe context of the Quasar Main Sequence, high Eddington rate sources are thosewhich have weak [O III] lines and strong Fe II lines. There is an overlapbetween the two populations, but they are not identical. Thus these twoselection criteria give a different view on which objects are actually highEddington ratio sources. We discuss this issue in the context of the broad bandspectral energy density, emission line shape modeling, Fe II pseudo-continuumstrength, and the level of X-ray variability. We also discuss the issue of theviewing angle and the insight one can gain from spectropolarimetricobservations. We conclude that there is no single driver behind the Quasar MainSequence, and the Eddington ratio of the source cannot be determined from thesource location on the optical plane alone. On the other hand, an expectedrange of AGN parameters combined with a simple model of the Fe II productionrepresent well the observed coverage pattern of the plane, with not much effectneeded from the dispersion due to the viewing angle.

Narrow-line Seyfert 1 galaxies in the context of the Quasar Main Sequence