The lack of an accepted rationale for the method seems to make people guilty about using lectures. At best they are taken for granted (but without any attempts to understand or improve them), at worst attempts are made to replace lectures almost anything else; even when alternatives involving small-group teaching, seminars, or tutorials are completely impractical and unaffordable in mass higher education systems. Even absurd gestures such as abandoning real teaching altogether and getting groups of students to ‘teach-themselves’ is regarded by some educationalists as an improvement on lectures.

But perhaps the most convincing evidence of lectures’ effectiveness comes from what people actually do, rather than what people say, because expressed-opinions have few costs or consequences are therefore are a less reliable guide to preferences than lived-choices. I find it highly significant that lectures are especially used in teaching the most quantitative and systematic sciences, and for intensive professional training courses such as medicine, engineering and law – lectures are less used (and less prestigious) in the arts and humanities such as literature and philosophy. In other words, lectures are a focus of teaching in exactly the situations where transmission of knowledge is most vital, and in subjects where learning is most easily and validly measurable. Of course, lectures will only get you so far, and individual teaching by ‘apprenticeship’ supported by self-directed study remain necessary for learning specialized and high level skills.

It is striking that, despite increasing choice of alternatives, the great majority of students continue to enrol in attendance-based and residential universities where lectures are a primary mode of instruction. And, when at university, they usually show-up for lectures, even when the lectures are not compulsory, and even when written hand-outs or transcriptions are available. (However, I believe that written material too closely-keyed into the specific lecture content probably has a tendency to undermine the effectiveness of lectures – see below).

Students still choose lecture-based teaching despite the ready availability of cheaper and more convenient alternative qualifications from highly-reputable 'distance learning' institutions which have grown-up to exploit new communication technologies as they were invented. Postal correspondence courses were popular from the early twentieth century. The UK Open University added TV and radio broadcasting to the postal system. More recently, the massive and expanding University of Phoenix in the USA has used e-mail and internet technologies. But although distance-learning is often both high in quality and reasonable in price, it has added to, rather than displaced, the demand for attendance-based, lecture-focused educational institutions. Apparently, many students experience difficulties in learning in solitude even from the finest written or audio-visual media.

Taking all these observations together, there seems to be ample prima facie evidence that lectures are probably the best practicable teaching method in many circumstances and for many students. However, it is not generally understood why lectures are useful, and the lack of a convincing rationale for lectures has been a major factor in under-estimating their importance. Because this rationale is not understood, the conduct of lectures has often been changed in ways that make them less effective – for instance inappropriate use of visual aids, and undermining the focus upon spoken lectures by excessive emphasis on written support material (eg. hand-outs and transcripts – nowadays often distributed by the internet).