  We have explored the spin liquid state in Tb2Ti2O7 with vibrating coil
magnetometry down to 0.04 K under magnetic fields up to 5 T. We observe
magnetic history dependence below $T < 0.2$K reminiscent of the classical spin
ice systems Ho2Ti2O7 and Dy2Ti2O7. The magnetic phase diagram inferred from the
magnetization is essentially isotropic, without evidence of magnetization
plateaux as anticipated for so-called quantum spin ice, predicted theoretically
for [111] when quantum fluctuations renormalize the interactions. Instead, the
magnetization for $T \ll T*$ agrees semi-quantitatively with the predictions of
"all-in/all-out" (AIAO) antiferromagnetism. Taken together this suggests that
the spin liquid state in Tb2Ti2O7 is akin to an incipient AIAO-antiferromagnet.
