  High resolution optical and infrared (IR) echelle spectra of the naked
(diskless) T Tauri star Hubble 4 are presented. The K band IR spectra include 4
Zeeman sensitive Ti I lines along with several magnetically insensitive CO
lines. Detailed spectrum synthesis combined with modern atmospheric models is
used to fit the optical spectra of Hubble 4 in order to determine its key
stellar parameters: Teff = 4158 +/- 56 K; log(g) = 3.61 +/- 0.50; [M/H] = -0.08
+/- 0.05; vsini = 14.6 +/- 1.7 km/s . These stellar parameters are used to
synthesize K band spectra to compare with the observations. The magnetically
sensitive Ti I lines are all significantly broadened relative to the lines
produced in the non-magnetic model, while the magnetically insensitive CO lines
are well matched by the basic non-magnetic model. Models with magnetic fields
are synthesized and fit to the Ti I lines. The best fit models indicate a
distribution of magnetic field strengths on the stellar surface characterized
by a mean magnetic field strength of 2.51 +/- 0.18 kG. The mean field is a
factor of 2.0 greater than the maximum field strength predicted by pressure
equipartition arguments. To confirm the reality of such strong fields, we
attempt to refit the observed profiles using a two component magnetic model in
which the field strength is confined to the equipartition value representing
plage-like regions in one component, and the field is allowed to vary in a
cooler component representing spots. It is shown that such a model is
inconsistent with the optical spectrum of the TiO bandhead at 7055 Angstroms.
