A survey of excitation function and angular distribution data for fast-neutron inelastic scattering on the principal even-even actinide nuclei considers first the ²³²Th(n,n') reaction from threshold to E_n=3.4 MeV featuring (total angle-integrated and differential) level cross sections for rotational or (quadrupole/octupole) vibrational states up to an excitation energy E*=1218 keV. Subsequent papers are similarly devoted to ²³⁸U and ^240,242,244Pu, respectively. Experimental data from (n,n' gamma ) and (n,n') measurements covering 28 such levels are contrasted with theoretical calculations from a 'standard' (CN+DI) treatment and from a statistical S-matrix approach, and with ENDF/B-V evaluations over the transition region in which a predominantly compound-nucleus (CN) mechanism is supplanted by direct interaction (DI). The data primarily comprise the latest findings by the Lowell group (1976) and update previous reviews. The results evince fair agreement with those of other groups and demonstrate the predictive capabilities of the statistical S-matrix (HRTW) formalism due to Hofmann, Richert, Tepel and Weidenmuller (1975) with interchannel coupling of collective states for the evaluation of a CN ('fluctuation') admixture in the presence of DI ('non-fluctuation') contributions.