Good and evil
The morality plays, according to Bevington's definition, concern themselves with "a conflict between... abstractions representing good and evil", and in one sense, this conflict is the central one. Though the leaf from the manuscript is missing where it would perhaps have been expressly stated, the play itself is basically a conflict between the force of good (Mercy) and the forces of evil (Mischief, the three vices and Titivillus) with the soul of Mankind as a prize.
Textual translation and exegesis
With allegorical characters, a writer automatically foregrounds the problem of how you read what you see, and how you interpret something. This play, though, regularly foregrounds the idea of language: Mercy, for example, is regularly parodied and imitated by the three vices, who even go so far as to deliberately mis-interpret and mis-translate Biblical Latin. It is a play which takes real pleasure in language, and, perhaps inevitably, is incredibly interested therefore in words and meaning.
The audience
Mankind, of course, represents all mankind, but the play Mankind, more than any other morality play that survives, takes huge pains to involve and include the audience in its theatrical action. The audience are expected to pay up in order to see Titivillus made visible, and they are even hoodwinked into joining in the vices' Christmas song - not realising, of course, at first, how rude it is. In being a play about Mankind, the play is also a play about mankind - about all of us - and there is therefore a tight thematic unity in the way the play considers and appropriates the audience into its theatricality.
Work versus idleness
"The devil makes work for idle hands", the proverb tells us, and it is made very clear from the start in this play that the way to fend off vice and sin is to work. Mankind, who initially associates himself (and therefore humanity as a whole) with clay and earth, is a manual laborer, tending his patch of land and growing his corn - and the symbolism is all too clear when the vices are beaten away using Mankind's own hard-handed implement of labor: his spade. References to work abound in this play - Mischief even tells Mercy he has come as a winter corn-thresher - and it is even possible that it might have been performed in front of a working community of some description.
Game and earnest
"Game", in the medieval period, was used to refer to the comic, the frivolous and the lighthearted, and was often contrasted with "earnest", which represented the more serious and sententious. This play as a whole is a rich blend of comic, ripe, rude, bawdy (often physical) humor with serious moral lessons, and the combination of characters like Mercy (earnest) with characters like Nought (game) is stylistically a key dichotomy to explore.
Earthly versus spiritual
It is a central concern in this period that humans are concerning themselves with worldly things and not with their ultimate spiritual judgment - and whether they will dwell in heaven or hell. Mankind himself, of course, announces that he is composed "Of a body and of a soul, of condition contrary". The play constantly explores the conflict between worldly concerns, riches, clothes and relationships, and the need to focus on spiritual welfare, heaven and hell and God's judgment.
Transience
Many of the morality plays concern themselves with the idea that life on earth is transitory, and that spiritual life after death is what we should really focus on. Mercy at several points warns both Mankind and the audience that they should be thinking about God's judgment, and not focusing on the sort of earthly, 'live for the moment' (a translation, perhaps of Nowadays' name) japes that the three vices do. Life is transitory - always changing, always in transition, always moving towards death. Only heaven or hell is eternal.
