The CAST model of digital communication – Part 2

©, used under a Creative Commons licence, via Unsplash

In the previous article, I began to introduce my CAST model of communication, and explained the first stage.
In this article, I introduce the other three aspects of the model.

2. Audience

The second aspect of the CAST model is the audience. The audience is the end of the process in one sense, but it must never be the last point in my thinking. If I simply work sequentially from me to the audience, I am only considering the communication with reference to my interests, not to my audience's needs: What concept do I want to communicate? What do I think would be a good way of shaping this message? What do I want to use to transmit this? Such me-centred communication is never appropriate for Christian communicators.

Once I have my concept, therefore, the next stage is to consider what is best for my audience, not what is my preferred way of communicating it. That is likely to mean that I need to work much harder on shaping and reshaping the message to make it suitable for them.

We must work hard to understand our audience rather than making assumptions about them. Consider factors like their

  • culture
  • socio-economic background
  • gender
  • age
  • literacy
  • language
  • technological competence
  • use of social media
  • occupation
  • leisure activities

We need to consider how our audience is likely to respond1 to the concept we are communicating and to the way we shape the message.

3. Shape

Once I have a good grasp of the concept I want to communicate, and a good understanding of my audience, I can begin to construct my message in a form which my audience can respond to.

To construct the message, we will draw on various semiotic resources: there are signs and modes available for us to use.
The available semiotic resources and the concept itself need combining together to create the message. This is the process of shaping.

We need to do our best to shape our message in the best possible way so that our audience will engage with it, understand it, and respond to it. The goal is that their lives are changed. This is the point of Christian communication: not that we can be self-satisfied about our communication strategy or social media presence, but that God's kingdom grows. So how do we shape this message in order to bring about changed lives? What is the best way to shape my message for this audience?

I need to ask questions like:

  • What ideas do I need to include?
  • What are the best words for me to use?
  • What is the best mode to communicate this – speech, written text, video, etc.?
  • How do the signs I might use function in my audience's cultural context
  • What images will work?

It is vital, as part of this, to think about which modes provide the most appropriate affordances. As we saw in part one of this series, affordances are the qualities a mode has – what it enables you to say. A handshake is a good mode for communicating 'welcome' or 'it's good to see you again' or 'we have agreed', but no good at all for communicating 'I'm confused' or 'that's a beautiful sunset'.

We need to consider, then, which mode or modes will give us the combination of affordances we need to be able to communicate our concept effectively to the audience. If we want to express love to someone, we will want to have a wide range of affordances at our disposal. Sending messages via Morse code might be amusing (or even necessary in some circumstances), but is hardly likely to lead to a rich relationship. A handwritten letter has more affordances than a text message; a conversation over dinner has more affordances than a telephone call. But if we are communicating within the context of, say, a television news programme, a dinner-table conversation has the wrong affordances altogether. Instead, we need to be able to communicate seriousness, thoroughness, and impartiality.

Which affordances do we need, and therefore which modes should we be using, when communicating the gospel? It all depends on the context. A radio ministry, by definition, primarily uses broadcast speech. But the broadcaster can make its communication multimodal by including music or drama in its programmes, or by making use of social media or printed resources. Yet when communicating the gospel within a friendship, these modes may not be ideal.

Having decided on the modes with the most useful affordances, we then need to decide on what signs to use within each mode. We need to find the best words, the clearest or most potent images and symbols, the colours with the right psychological connotations, and so on.

The key question to ask is, how do I shape my message so that it best serves the needs of my audience in order for them to understand my message?

4. Transmission

Having shaped the message, we need to pass it on to our audience – to those we hope will be responders – through some kind of channel. This is the process of transmission, which is the final aspect of the CAST model. This is not necessarily in the sense of broadcasting, since in a face-to-face conversation we are still transmitting our message to the other person.

In the case of this article, since the means of transmission is the internet, I shaped my concept using the primary mode of text, but included some other modes: photographs, diagrams, and symbols. These can all easily be transmitted electronically via the internet and whatever web browser you are using to read this. Previously, this material was a lecture so the means of transmission was me speaking in a lecture theatre while projecting things on a screen. On that occasion, I combined the modes of speech and gesture as well as text, photographs, diagrams, and symbols. At some point, I could re-shape it again into a video presentation for transmission via YouTube.

The transmission aspect raises technological questions:

  • What technological tools and channels are available to me?
  • Which can I use well or easily or cost-effectively?
  • What technological tools and channels can actually reach this audience most effectively (which we may measure by numbers of people in the audience, or by the impact on them, or both)?
  • Which are the most appropriate for this audience?


The process of communication is, as we have seen, very complex. As Christian communicators, we have a responsibility before God to do it to the very best of our ability. And we have a responsibility to our audience to do our best to communicate our message to them as clearly and helpfully as we can so that their lives can be changed. If we fail to do so, it is a failure to love either God or our audience or both.

We start with our concept and work on that until we have the best understanding of it we can. Then we work to understand our audience as well as we can, so that we can work hard at shaping the message in the best possible way to suit both our concept and our audience. And finally, we must think carefully about how best to transmit our message so that our audience can encounter the message – recognise the prompt, engage with it, and do interpretive work on it.

The ultimate goal in all this is that lives are changed to the glory of God. That is a wonderful goal.


  1. Note that, from here on, I will generally refer to the audience as 'responders'. Kress refers to the audience as both 'recipients' and 'interpreters', but in my view the word 'recipient' is too passive unless some interpretation also takes place. The more active word 'responder' can cover both of those aspects. ↩︎

Image credits (from top), via
Diagrams by Tony Watkins

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