Hmmmm, maybe not this definition The Virginia Law RegisterThe Virginia Law Register > Vol. 12, No. 6 (Oct., 1906), p. 506Vol. 12, No. 6
Validity and Legitimation These adjectives describe assertions, arguments, conclusions, reasons, or intellectual processes that are persuasive because they are well founded. What is valid is based on or borne out by truth or fact or has legal force: a valid excuse; a valid claim. What is sound is free from logical flaws or is based on valid reasoning: a sound theory; sound principles. Something cogent is both sound and compelling: cogent testimony; a cogent explanation. Convincing implies the power to dispel doubt or overcome resistance or opposition: convincing proof.
The very act of participating in discourse, of attempting discursively to come to an agreement about the truth of a problematic statement or the correctness of a problematic norm, carries with it the supposition that a genuine agreement is possible. (Habermas, p xvi, 1973)
The structure is free from constraint only when for all participants there is a symmetrical distribution of chance to select and employ speech acts, when there is an effective equality of chances to assume dialogue roles. Thus, the conditions for ideal discourse are connected with conditions for an ideal for of life; they include linguistic conceptualisations of the traditional ideas of freedom and justice. “Truth”, therefore, cannot be analysed independently of “freedom” and “justice”. (Habermas, p xvii, 1973)
The exact nature of 'validity' is a highly debated topic in both educational and social research since there exists no single or common definition of the term. Therefore, in order to understand something of the range of meanings attached to 'validity', it is essential to review a selection of the range of definitions given by leading authors. A much cited definition of 'validity' is that of Hammersley's (1987, p. 69): "An account is valid or true if it represents accurately those features of the phenomena, that it is intended to describe, explain or theorise." Although this would seem to be an all-encompassing and reasonable description, many other definitions fail to envisage such a 'realist approach' (Denzin & Lincoln, 1998, p. 282). The fact that there are so many possible definitions and replacement terms for 'validity' suggests that it is a concept entirely relative to the person and belief system from which it stems. One of the most recurring features in critical discussions of 'validity' is the combination of 'validity' with the term 'reliability' (Campbell & Fisk as cited in Simco & Warin, 1997; Black & Champion, 1976, p. 222, 234; Kerlinger, 1964, p. 430; Hammersley, 1987, p. 75). Yet, the definitions for 'reliability' are as varied and as complex as those for 'validity'. Winter, G. (2000). A comparative discussion of the notion of 'validity' in qualitative and quantitative research The Qualitative Report, 4(3 & 4).
'validity' 'An agreement between two efforts to measure the same thing with different methods' -- Campbell and Fisk (as cited in Hammersley, 1987) 'The measure that an instrument measures what it is supposed to' -- Black and Champion (1976, pp. 232-234) 'Accuracy' -- Lehner (1979, p. 130) 'Degree of approximation of 'reality' -- Johnston and Pennypacker (1980, pp. 190-191) 'Are we measuring what we think we are?' -- Kerlinger (1964, pp. 430, 444-445) 'to the extent that differences in scores yielded…reflect actual differences' -- Medley and Mitzel (as cited in Hammersley, 1987, p. 150) Hammersley (1987) reviews the extent to which 'reliability' and 'validity' are defined by a selection of different authors writing from different methodological positions. I will avoid merely repeating those definitions verbatim and instead offer a few key words summarising each definition.
Reliability 'An agreement between two efforts to measure the same thing with the same methods' -- Campbell and Fisk (as cited in Hammersley, 1987) 'Ability to measure consistently' -- Black and Champion (1976, pp. 232-234) 'Reproductibility of the measurements…stability' -- Lehner (1979, p. 130) 'Capacity to yield the same measurement…stability' -- Johnston and Pennypacker (1980, pp. 190-191) 'Accuracy or precision of a measuring instrument?' -- Kerlinger (1964, pp. 430, 444-445) 'To the extent that the average difference between two measures obtained in the same classroom is smaller than…in different classrooms' -- Medley and Mitzel (as cited in Hammersley, 1987) Winter, G. (2000). A comparative discussion of the notion of 'validity' in qualitative and quantitative research The Qualitative Report, 4(3 & 4).
Insofar as 'validity' definitions are concerned, two common strands begin to emerge: Firstly, whether the means of measurement are accurate Secondly, whether they are actually measuring what they are intended to measure.
The notions of accuracy, more commonly attributed to 'validity', appear to be associated with 'reliability' also. What authors do seem to attribute to 'reliability' more commonly than to 'validity' is the degree of replicability.