Two kinds of inability (2): defect of the will itself
Thesis XIX. 'The second kind of inability arises from a lack in the will itself, that is, in the act of willing. If that willing were present in the measure it ought to be, the commandment would be kept with the greatest ease, for it is kept simply by willing firmly. So if someone wills firmly, the commandment is thereby already kept and cannot fail to be kept, since such a will carries with it both full willing and the power to do what it has willed.
'This inability to act does not excuse in the least the person who fails to do what is commanded, for he could do it if he chose. If he did not choose to, and so could not, who would deny that he deserves blame for that very will, so perverse and hardened?'
Latin
XIX. Altera impotentia est quae ex defectu ipsius voluntatis, seu volitionis oritur, quae si adesset, quanta adesse debet, praeceptum facillime impleretur. Tantummodo enim fortiter volendo impletur, unde si fortiter vult, hoc ipso jam impletum est, & non impletum esse non potest. Talis enim voluntas sicut secum affert plenum velle, ita & posse quod voluit. Haec impotentia faciendi nullo modo excusat eum, qui non implet quod praecipitur. Posset enim implere si vellet. Quod si noluerit, atque ideo non potuerit, quis non eum dixerit, pro ipsa tam perversa obdurataque voluntate culpandum?