There are two main kinds of persons in fiction ;
those whose characters do not change, but whose natures are disclosed by the story (like Lady Macbeth) ;
and those whose characters do undergo a change, whether for bet¬ter or for worse (like Tess).
The former are sometimes called static characters, and the latter, dynamic. Kip¬ling's Mulvaney is static, Stevenson's Markheim is dy¬namic.
Outward action is often preceded by struggle of soul, marking character transformation. Sometimes, as with Hester Prynne in The Scarlet Letter, that struggle is with the lower nature, striving more and more effectively to rise above it. Sometimes the battle is with the higher nature, deterioration being the result, as in Tito Melema, of Romola. Again the war is waged with external forces, as in Hamlet's bitter problem of how to do justice in a case which involved his own mother. But somehow, always, character-change must involve, suggest, or dis¬close, a force big enough to account for the result. It is ridiculous for an author to transform a character by sheer hocus-pocus, or suddenly attribute a momentous deed, good or bad, to a character whose qualities all point the other way.
Critical times in the action fittingly coincide with moral crises in the characters. Remember that some incidents reveal character, while some affect character. Ask these questions : Could such a woman, let us say, being al¬together such as she is, do such a deed as you propose to make her do? Next, would she do it? Finally, can no more effective thing be devised ? Study " The Out¬casts of Poker Flat " and see how character transforma¬tion is satisfactorily accounted for.