θέσις or thesis

Thesis is the 13th exercise in the ancient progymnasmata and deals with arguments.  According to Theon, thesis "is a verbal inquiry admitting controversy without specifying any persons and circumstance; for example, whether one should marry, whether one should have children, whether the gods exist." (Theon 120, Kennedy).

Thesis differs from topos in that a topos is a stock argument about which there is great agreement.  Thesis on the other hand is a proposition about which there is disagreement.  Theon says that one can get the subject of a thesis from a maxim, proverb, chreia, or another useful saying.

After coming up with the thesis itself, the student would attempt to either confirm or refute the thesis.  One can confirm or refute according to a number of topoi, such as, is the thesis possible, necessary, beneficial, pleasant, praiseworthy, etc.

In Luke chapter 20, the Lukan Jesus engages in the refutation of a thesis using the topos of possibility.

In 20:41, Jesus asks:  “How can they say that the Messiah is David’s son?  The thesis presupposed here is that the Messiah is said to be the Son of David.

Jesus then goes on to refute even the possibility of this claim from the topos of impossibility as follows:

For David himself says in the book of Psalms,
    ‘The Lord said to my Lord,
    “Sit at my right hand,   
until I make your enemies your footstool.” ’
 David thus calls him Lord; so how can he be his son?”  (Luke 20:42-44).

Jesus has claimed that it is impossible for David to call his son "Lord."  Here Luke has engaged in the simple preliminary exercise of thesis and has used it to great effect in his Gospel.