I have spent most of my life teaching ESP, especially EAP and in talks that I have given and courses that I have run, I’ve always given three strong reasons for teaching ESP or ESAP as opposed to general English or EGAP. The first is linguistic – different subjects use different language. There is a large amount of research evidence for this – see, for example, Hyland (2011, 2012). The second is to do with knowledge transfer: the nearer you can get to the student’s ultimate reason for learning English, the more likely it will be that the student will be able to make use of what you are teaching in the new context (see, for example, Dias, Freedman, Medway & Paré, 1999; Willingham, 2007; James, 2014, Bharuthram & Clarence, 2015). The third is motivation. This is something that everyone seems to agree with (see, for example, Stevick, 1976; Krashen, 1982; Wenden, 1981). – that students will be more motivated when the English course is directly related to their main subject course or professional needs (intrinsic rather than extrinsic motivation (Deci & Ryan, 1985) or ideal self compared to ought-to self (Dornyei, 2009, 2010) – so I’ve never felt the need to justify it. Students do not see the learning of a subject separately from the learning of the language of that subject: Learning the content of a subject means learning the language of that subject. As Ushioda (1998) points out:
…the language learner, unlike the researcher, seems unlikely to perceive the motivation for language learning to be wholly independent of the motivation (or lack of motivation) for other areas of learning (p. 83).