i. By its oblique cases the gerund (and the gerundive in the

construction mentioned above--the ‘gerundival attraction’) completes the active infinite verb noun, which is only used in the nom. and acc., e.g. _haec ad iudicandum sunt facillima_, ‘these matters are very easy to decide’; _amor agendi, canendi_, etc., ‘love of acting, singing,’ etc.; _causâ agendi_, ‘for the sake of acting’; _aqua utilis bibendo_, ‘water useful for drinking’; _mens alitur discendo_, ‘the mind is nourished by learning.’

ii. The nom. (and in _oratio obliqua_ the acc.) of the gerund is used intransitively with parts of the verb _sum_ (_est_, _erat_, _fuit_, _esse_, etc.), as an impersonal verb to denote necessity, duty, or suitability, e.g. _nunc est bibendum_, ‘now it is right to drink’, _eundum est_, ‘there is a necessity to go’; _parendum est legibus_, ‘it is necessary to be obedient to the laws.’ The person on whom the duty falls is expressed by the dat. case, the ‘Dative of the Agent,’ except after verbs which govern a dative; after these, to avoid ambiguity, the agent is expressed by _a_ or _ab_ with the abl., e.g. _eundum est mihi_, ‘I must go,’ but _parendum est ei a te_, ‘you must obey him’.