  We develop a unification scheme which explains the varied observed properties
of TDEs in terms of simple disc physics. The unification scheme postulates that
the different observed properties of TDEs are controlled by the peak Eddington
ratio of the accretion discs which form following a stellar disruption. Our
primary result is that the TDE population can be split into four
subpopulations, which are (in order of decreasing peak Eddington ratio):
"obscured" UV-bright and X-ray dim TDEs; X-ray bright soft-state TDEs;
UV-bright and X-ray dim "cool" TDEs; and X-ray bright hard-state TDEs. These 4
subpopulations of TDEs will occur around black holes of well defined masses,
and our unification scheme is therefore directly testable with observations. As
an initial test, we model the X-ray and UV light curves of six TDEs taken from
three of the four subpopulations: ASASSN-14ae, ASASSN-15oi, ASASSN-18pg,
AT2019dsg, XMMSL1 J0740 & XMMSL2 J1446. We show that all six TDEs, spanning a
wide range of observed properties, are well modelled by evolving relativistic
thin discs. The peak Eddington ratio's of the six best-fitting disc solutions
lie exactly as predicted by the unified model. The mean stellar mass of the six
sources is $\left\langle M_\star \right\rangle \sim 0.24 M_\odot$. The
so-called `missing energy problem' is resolved by demonstrating that only $\sim
1\%$ of the radiated accretion disc energy is observed at X-ray and UV
frequencies. Finally, we present an empirical, approximately linear,
relationship between the total radiated energy of the accretion disc and the
total radiated energy of an early-time, rapidly-decaying, UV component, seen in
all TDEs.
