If +tat+ in Sanskrit is +ta+ + +ta+, then we expect in Gothic _tha_ + _tha_, instead of which we find _tha_ + _ta_. We expect in Latin _istut_, not _istud_, _illut_, not _illud_, _it_, not _id_, for Latin represents final _t_ in Sanskrit by _t_, not by _d_. The old Latin ablative in _d_ is not a case in point, as we shall see afterwards. Both Gothic _tha-ta_, therefore, and Latin _istud_, postulate a Sanskrit +tad+, while Zend and Greek at all events do not conflict with an original final media. Everything therefore depends on what was the original form in Sanskrit; and here no Sanskrit scholar would hesitate for one moment between +tat+ and +tad+. Whatever the origin of +tat+ may have been, it is quite certain that Sanskrit knows only of +tad+, never of +tat+. There are various ways of testing the original surd or sonant nature of final consonants in Sanskrit. One of the safest seems to me to see how those consonants behave before +taddhita+ or secondary suffixes, which require no change in the final consonant of the base. Thus before the suffix +îya+ (called +cha+ by Pâṇini) the final consonant is never changed, yet we find +tad-îya+, like +mad-îya+, +tvad-îya+, +asmad-îya+, +yushmad-îya+, etc. Again, before the possessive suffix +vat+ final consonants of nominal bases suffer no change. This is distinctly stated by Pâṇini, I. 4, 19. Hence we have +vidyut-vân+, from +vidyut+, lightning, from the root +dyut+; we have +udaśvit-vân+, from +uda-śvi-t+. In both cases the original final tenuis remains unchanged. Hence, if we find +tad-vân+, +kad-vân+, our test shows us again that the final consonant in +tad+ and +kad+ is a media, and that the _d_ of these words is not a modification of _t_. Taking our stand therefore on the undoubted facts of Sanskrit grammar, we cannot recognize _t_ as the termination of the neuter of pronominal stems, but only _d_;[24] nor can we accept Bopp’s explanation of +tad+ as a compound of +ta+ + t, unless the transition of an original _t_ into a Sanskrit and Latin _d_ can be established by sufficient evidence. Even then that transition would have to be referred to a time before Sanskrit and Gothic became distinct languages, for the Gothic _tha-ta_ is the counterpart of the Sanskrit +tad+, and not of +tat+.