It's a commonplace that the art historian is related to the detective. I find the pervasiveness of this analogy interesting, and although I am by no means a believer in astrology, I was mildly amused to see that the trope of art-historian-as-sleuth had even penetrated into that murky field when I read that a Scorpio (which I am, coincidentally) is ideally suited to work such as crime scene forensics, depth psychology, investigative journalism, espionage, police or private detective work, and art historians. Presumably there is something forensic and interrogative about the methodology of that traditional connoisseurial-biographical school of thought which even today (i.e. even after formalism, iconography, social history, feminism, psychoanalysis, semiotics, cultural studies, structuralism, queer theory, post-structuralism, postcolonialism, visual culture and 'the iconic/pictorial turn' have all had their methodological impact) tends to typify the art historian in popular imagination. The persistence of the myth also probably owes something to the stock cinematic bow-tied curator, invariably male, fastidiously interrogating documents and images through half-moon glasses, which for many people outside of the discipline could well mediate their impressions. As is the case with many contemporary mythologies, a compound of historical realities with earlier mythologies is at play.
Museums, Morelli said, are full of wrongly attributed paintings – indeed assigning them correctly is often very difficult, since often they are unsigned, or painted over, or in poor repair. So distinguishing copies from originals (though essential) is very hard. To do it, said Morelli, one should abandon the convention of concentrating on the most obvious characteristics of the paintings, for these could most easily be imitated – Perugino's central figures with eyes characteristically raised to heaven, or the smile of Leonardo's women, to take a couple of examples. Instead one should concentrate on minor details, especially those least significant in the style typical of the painter's own school: earlobes, fingernails, shapes of fingers and toes.
As Ginzberg states (p.8), it was Enrico Castelnuovo who compared Morelli's method of classification to that attributed by Arthur Conan-Doyle to his fictitious creation, Sherlock Holmes. Castelnuovo developed this comparison upon the basis of an observation made by Edgar Wind:
Morelli's books… look different from those of any other writer on art; they are sprinkled with illustrations of fingers and ears, careful records of the characteristic trifles by which an artist gives himself away, as a criminal might be spotted by a fingerprint . . . any art gallery studied by Morelli begins to resemble a rogue's gallery'. 
Wind also explained Morelli's fascination with the seemingly minor anatomical details of painted human figures as having a Freudian basis:
To some of Morelli's critics it has seemed odd that personality should be found where personal effort is weakest. But on this point modern psychology would certainly support Morelli: our inadvertent little gestures reveal our character far more authentically than any formal posture that we may carefully prepare.
Sigmund Freud himself acknowledges the early influence of Morelli upon him (under the pseudonymous guise of a supposed Russian art connoisseur Ivan Lermolieff) long before developing psycho-analysis. However, Michael Hatt and Charlotte Klonk seem to feel that Freud over-psychologised in his understanding of Morelli's method. That is to say, Freud (and by implication those scholars who have made something of Freud's acknowledgement) misunderstood Morelli's drive to anatomise, catalogue and taxonomise painted details. Rather than assuming a 'parapraxic' unconscious expressiveness secretly at work in those moments when a painter is least focused on representing a body part, Morelli's method was in fact indebted to the palaeological practices and methodologies of Cuvier and Agassiz (the latter of which Morelli knew personally). This was owing to Morelli's desire to develop, by analogy with the typological methods of palaeology, a typology of his own: one which collated painters' personal mannerisms without having to rely on biographical or documentary detail external to the works of art they had produced.
Ginzberg reads Morelli's method through a Freudian optic, in which cultural stylistic constraints are at a minimum, and individual mannerism at a maximum, when the artist is most relaxed. While the two termed relation between individual manner and stylistic constraint implied here is typical for the intellectual milieu in which Morelli theorised, it was far from accepted that the two terms were necessarily antagonistic, such that only the recession of a consciousness of cultural constraints could allow for the personal manner to 'escape' and have its expression. On the contrary, Carl Friedrich von Rumohr's art-historical theory claimed that the great painters were those who had harmonized these two terms in a single, unified and universal expression.
Nonetheless, Freud's purported misreading must have been highly productive, for he mentions two distinct encounters with Morelli's 'method' which informed his thinking, as if it foreshadowed, if not constituted, something of a partial theoretical prototype.. As a theory that the overlooked, marginal, residual, and habitually disregarded elements, rather than the culturally-determined focii of a production, can yield valuable information about the inner life and thus the singularity or identity of its producer, however, it does not translate at all well into modern (post-Lacanian) psychoanalytic theory, for whom the figure of the subject with a rich and highly individualised 'inner life' is just another way in which the objet a directs desire and avoids confrontation with the 'subjective destitution' to be found in confrontation with the subject proper: le sujet barré. Thus there is a sense in which Freud's rendering of Morelli's method not only does not presage or inform actually-existing contemporary psychoanalysis, but indeed presents it only with misconception and misinformation. Furthermore, Morelli's method appears far from practicable, and indeed was not used by Morelli himself. Rather, it appears in the form of a fantasy which Morelli had about himself, with enough self-consciousness to have at first concealed the name of its author, only later acknowledged. We might even speak of Freud's fantasy of discovery, of uncovering the origins of his own disavowed thinking. It's a rewarding exercise to 'discover' apparent precedents for present thinking in the detritus of memories of encounters and readings, but self-excavation is at least as much construction as it is uncovering. The past is always reconstituted in the present that it is the past of, as the neuroscience of plasticity and memory consolidation tells us: the only anchors to be found in a life-history are those summoned by the requirements of a present crisis in meaning. On the other hand, social history has a verifiable solidity that can be gauged through collective signatures and cultural deposits.
The problem of attributing 'the method', and the idea of a method, destined to be itself regarded as 'a cure' for the problem of misattribution, appears in this regard circular and threatens to spill over into a general epistemological problem of authorship and origins in general. However the mention of 'cure' is not merely rhetorical here: as Ginzberg notes, both Freud and Morelli were indeed physicians. The trio is completed by Conan-Doyle, a physician by training and the third figure included in Ginzberg's model of historical detectives, owing to the literary figure Sherlock Holmes' abiding fascination in the truth-bearing capacity of 'trifles'. Medical epistemology is based upon the identification of a malady through the observation and collation of 'symptoms' — the same term which Freud used in his developing metapsychology. Ginzberg goes further, then, than simply reading Morelli's method in a Freudian optic. Rather, he gestures towards a medical 'paradigm', in which symptoms form a system of signification, underlying both Freud and Morelli. We could broaden this intuition, and thus partially rehabilitate Ginzberg's exposition, against Hatt and Klonk, by further indicating that medical science and palaeology are both premised upon a broader context of empirical semiotics, which is precisely the direction in which Morelli was trying to move art history: towards a science of observation in which a series of empirically observed signifiers would indeed prove in themselves significant, productive of meaning-laden information, verification of identity and thus ultimately productive of knowledge and value to a community of peers. Morelli's desire to provide a self-contained empiricism, or at least a scientific method, for the practice of identifying art-work can be read both as an attempt to institute the same attentive observation of significant identifying details as that found in the taxonomy of fossils, and as a desire related to that of Freud in his early search for a method, close to that of medicine and the practice of physicians observing symptoms of illness, for an as-yet undeveloped science of 'reading the signs' of an unconscious psychology. The issue is one of stoically asserting a significance to the unassuming and insignificant: of carefully regarding the disregarded. For the doctor of medicine, the symptom is significant: given its constellation with certain other symptoms it may point to a cause. In a painting, sculpture, monument or work of art the overlooked detail can be significant: in concert with others it may even help to verify its origins. Freud's parapraxes, by analogy, reveal the operation of an unconscious desire and perhaps a repressed history (or what we could justifiably call a 'prehistory'). The palaeologist's found fossil bears markings or a form which is used as a signifier, read as a sign pointing to the catalogue and its taxonomy of prehistopric species. These semiotic systems indeed share a much broader and common epistemological paradigm, which is that of producing knowledge through the legibility of signs inscribed as painted canvas, sculpted stone, body, bone, speech or utterance.
Hatt and Klonk's historical precision in tracing Morelli's method to a certain palaeological influence may indeed identify a stronger element in Morelli's no-doubt mixed and syncretic thought processes, however the method itself is somewhat overdetermined by an entire historical paradigm of looking for clues and symptoms to be read as signs pointing to, indicating, or bearing revelatory content, about the provenance of a body they belong to. An iconological fever, in which all of nature and culture must be made to speak of itself, to produce from its own body a readable or intelligible account of its genesis, typifies the European historical period spanning from the early modern to the contemporary. The endless importance of trifles, the intense questioning of a parapraxic slip or lazily-drawn earlobe is a sub-current of that great tide. The search for a methodology is something that has always typified art history in this period; practitioners might well be compared with Duke Senior in the Forest of Arden in Shakespeare's As You Like It, who claims to finds 'tongues in trees, books in running brooks' and 'sermons in stones'. The hermeneutic problem, in Shakespeare's Arden as in reality, is that the Book of Nature is susceptible to heterogeneous readings. Is this also the case with an analogical Book of Culture(s)? Or does the historicity of human culture make a difference, make it approach something more stable and significant in itself? You can never really shake free of Hegel in this business.
 Ginzberg 1980:7
 Wind 1985:38 in Ginzberg 1989:97-98
 Freud 1959:270–71 in Ginzberg 1989:99
 Hatt & Klonk 2006:51
 Ginzberg 1989:99-100
Freud, Sigmund, 1959, 'The Moses of Michelangelo', Collected Papers, vol.4, Basic Books, London, pp. 270–71
Ginzburg, Carlo, 1980, 'Morelli, Freud and Sherlock Holmes: Clues and Scientific Method', History Workshop, No. 9 (Spring, 1980), pp. 5-36, Oxford University Press, available at http://www.jstor.org/stable/4288283 accessed 21/11/2010
Ginzberg, Carlo, 1989, Clues, Myths and the Historical Method, Johns Hopkins University Press
Hatt, M. & Klonk, C., 2006, Art History: A Critical Introduction to its Methods, Manchester University Press
Wind, Edgar, 1985, Art and Anarchy, Northwestern University Press