Intertextuality - Hays Criteria and Assumption

Richard B. Hays in his celebrated work, Echoes of Scripture in the Letters of Paul, offers seven criteria for determining an “echo” or an “allusion” to Scripture.

1. Availability: Was the proposed source of the allusion/echo available to the author and/or original hearers?
2. Volume: What is the degree of explicit repetition of words or syntactical patterns?
3. Recurrence: How often does Paul elsewhere cite or allude to the same scriptural passage?
4. Thematic Coherence: How well does the alleged echo fit into the line of argument that Paul is developing?
5. Historical Plausibility: Could Paul have intended the alleged meaning effect?
6. History of Interpretation: Have other readers, both critical and pre-critical, heard the same echoes?
7. Satisfaction: Does the proposed reading make sense?

Intertextuality is built on several key assumptions, which Hays outlines below.   

Prominent among these conventions are the convictions that a proposed interpretation must be justified with reference to evidence provided both by the text’s rhetorical structure and by what can be known through critical investigation about the author and the original readers. Any interpretation must respect these constraints in order to be persuasive in my reading community. Claims about intertextual meaning are strongest where it can credibly be demonstrated that they occur within the literary structure of the text and that they can plausibly be ascribed to the intention of the author and the competence of the original readers.

The concept of allusion depends both on the notion of authorial intention and on the assumption that the reader will share with the author the requisite “portable library” to recognize the source of the allusion…

This last quote is the achilles heel in many claims to intertextuality, as many of the audiences to whom New Testament authors wrote, simply did not have that "portable library" to recognise, recall, connect, assess and trust Paul’s intertextual reading.  And without this ability, claims to intertextuality are severely weakened and often undermined.