The death of US Supreme Court Justice Antonin Scalia has occasioned widely differing appraisals of his judicial legacy. But one difficulty which they all run up against, regardless of their scholarly, ideological, or political perspective, is the vast and pervasive set of ambiguities found in descriptions of Scalia's methodological approach to the interpretation of legal texts - including his own.
Here is an attempt at a bit of housekeeping.
The first point to be made is that we should dispense immediately with the term "Textualism", as it is utterly uninformative.
Progress then depends on clearly drawing a series of distinctions:
Originalism vs. (for lack of a better word) Contemporaneanism
Intent vs. Plain- (or Ordinary-) meaning vs. Audience-understanding
Literalism vs. (again for lack of a better word) Reasonablism
The first two sets of distinctions cut across one another.
We could be Intentionalists, and take the meaning of a legal text to be determined by the linguistic intentions of the text's author(s) - and here is an important and thorny complication, as modern legal texts must be seen as having either group authorship, or institutional authorship, where an institutional author is a kind of fiction - at the time the text was authored (in which case we would be Originalists, and more specifically Intent-Originalists); or, we could take the meaning to be what the author(s) would most probably, on the balance of whatever evidence is available, intend for the words they wrote to mean if they had written them today.
Likewise, we can take the meaning of the text as being whatever its plain meaning was at the time it was written, or as being what its plain meaning is today.
Finally, we can take the meaning of legal texts as being what, on the balance of evidence, their original audience understood or interpreted them as being - in the case of the Articles and Amendments of the US Constitution, that would be the (multiple) understanding(s) of the State legislatures - as groups or as institutions - which ratified them; or, we can take the meaning of legal texts as being whatever a contemporary reasonable and informed person would interpret it as being.
Literalism and Reasonablism are subtypes of a Plain-meaning approach to interpretation, which become relevant when the text to be interpreted is ambiguous or vague - i.e. when it has no plain meaning.
The Literalist will insist (as the moniker suggests) on a (maximally) literal interpretation of the text (however bizarre such an interpretation might be in context), on the assumption that there is always a single (most) literal interpretation, however ambiguous or vague a text may be. This literal interpretation could be an interpretation given the literal meanings of the words used at the time of authorship, or in the present day.
The Reasonablist, on the other hand, will revert to a version of the Audience-understanding interpretive approach at this point, and take the text to mean what a reasonable and relevantly informed person - that is, one who is linguistically informed about the text, who is familiar with any technical or specialized vocabulary, archaic uses and meanings of words, unusual phrases, rare grammatical constructions, etc. - either at the time the text was authored, or in the present day, would interpret it as meaning. Being informed, for the purposes of this interpretive theory, does not extend to having knowledge of the deliberative history of the text's production, the express or implied intentions of its authors, its most likely purpose given the socio-cultural-politico-economic context in which it was written, etc. And, since Reasonablism is a subtype of the Plain-meaning interpretive approach, it conceives of a purely hypothetical reasonable and informed person, and is not concerned with the actual understanding of any person, group, or institution, historical or contemporary - unlike a pure Audience-understanding theory.
A term which is frequently bandied about without being precisely defined is "Strict Constructionism". The closest we can come to a precise definition of it is: (a) the approach to the interpretation of legal texts which embraces Plain-meaning interpretation in the absence of vagueness or ambiguity; and (b) Literalism in the presence of vagueness or ambiguity. Strict Constructionists could, in theory, have either original or contemporary meaning in mind, since that distinction is, again, orthogonal to the others.
With all these distinctions in place, we can finally identify Scalia's (purported) approach to the interpretation of law: Plain-meaning-Originalism, Reasonablism sub-type. Whether he consistently adhered to that approach is another question entirely.
For the critic of Scalia's legacy - and I count myself as one - there are four main problems with the corpus of judicial decisions he leaves behind.
The first problem is the incredibly problematic assumption that, when a legal text does not have an (obviously, self-evidently) "plain" meaning, there is such a thing as the interpretation which a reasonable and informed person would give of it. See, for example, Richard Posner's blistering critique of Scalia's interpretation of the word "sandwich".
Understanding the second problem requires one more distinction: that between the interpretation of a legal text (which is all we've talked about thus far), and the application of the text's meaning to a question before the court.
For many legal controversies which were not foreseen by anyone at the time that the laws which would eventually become relevant to them were written - such as the controversy over affirmative action laws and public policies - neither the original plain-meaning of the legal text (if there is one), nor the reasonable and informed person's interpretation of it at the time it was authored (if there isn't), provides anything approaching determinate guidance of how the contemporary question is to be resolved. Accusations of Scalia's pomposity are justified by his capacity to support his (politically or religiously) preferred applications of the law by mere bluster, when the actual results of his (professed) interpretive method are entirely indeterminate.
This is in sharp contrast to other, non-Originalist interpretive approaches, such as Joseph Raz's Moderate Actual Institutional Authorial Intent approach, and Aharon Barak's Purposive approach, for which problems of contemporary application are much less severe.
The third is a problem not with Scalia's method itself, but with his execution of it: the fact that he - like many others - often did such a shoddy job of the historical linguistic work on which that approach depends, in order to create an illusion of legal justification for a preferred conclusion. Nowhere was that unfortunate tendency more egregiously displayed than in his majority opinion on gun control.
The fourth, and largest, problem is a philosophical/normative difficulty with Scalia's theory - a problem from an external perspective, rather than a problem of the theory's internal cogency, its applicability, or his execution of it.
There are good reasons - set out in the works linked to above, among other places, for rejecting the idea that the task of interpreting legal texts is a search for their plain meaning; rather, it is a search for something like their purpose, an understanding of what problem they set out to solve, and why they set out to solve it in that way.