That thou affirm confidently (se diabebaiousthai). Indirect command. For the verb see note on 1Ti 1:7.
That they may be careful (hina phrontizōsin). Sub-final use of hina with present active subjunctive of phrontizō, old verb, only here in N.T.
To maintain good works (kalōn ergōn pro‹stasthai). Present middle infinitive of proistēmi, intransitive use, to stand before, to take the lead in, to care for. Paul is anxious that “believers” may take the lead in good works.