These are some of the bigger issues I think about from time to time.
1. Practically all buildings are unique, therefore as architectural historians we generally work with anecdotal data. In other words, it's storytelling.
a. Broader claims are very difficult, because they tend to be either too obvious to be insightful, or too easily contested.
b. "Big data" may open new avenues.
c. Even when good data exists, architectural historians have a dubious but powerful tradition of waving away counter-evidence, because the exception proves the rule. As Ruskin said: "Corrupted forms ... only serve to show the majesty of the common design." (source)
d. I don't think the 'storytelling' aspect diminishes the enterprise. In fact I think for the most part I would like to embrace that and to craft stories that resonate and illuminate larger themes.
On storytelling, Dell Upton wrote: "What makes our work interesting is that the buildings about which we spin tales were made and used by men and women with stories of their own to tell. The historian's challenge is to choose which of many possible stories to tell and to decide how to integrate our stories with theirs." (source)
2. Problems of categorization have always been endemic. We elide this issue today by pretending that it's old-fashioned to categorize things, but we'd be better off to confront the issue.
a. Historians often write about style as if it were established in advance and imposed by the architect as his or her overriding concern. However, most architects insist that style is not prescriptive, rather it is the outcome of a process of searching.
1. Ted Cullinan's reflection here is the best expression of this that I know.
2. Then there is this excellent passage from Matthew Frederick's 101 Things I Learned in Architecture School:
"True architectural style does not come from a conscious effort to create a particular look. It results obliquely—even accidentally—out of a holistic process.
The builder of an American colonial house in 1740 did not think, as we often do today, 'I really like colonials, I think I’ll build one'. Rather, houses were built sensibly with the materials and technology available, and with an eye sensitively attuned to proportion, scale, and harmony. Colonial windows had small, multiple panes of glass not because of a desire to make a colonial-looking window, but because the technology of the day could produce and transport only small sheets of glass with consistency. Shutters were functional, not decorative; they were closed over windows when needed to provide shade from the sun. The colonial architecture that resulted from these considerations was uncalculated: Early American houses were colonial because the colonists were colonial."
3. And I love this quotation from the introduction to Governing by Design, by Daniel M. Abramson, Arindam Dutta, Timothy Hyde, and Jonathan Massey:
"Rather than affirming the continuity from architect’s intention to realization in the completed building, or confirming master narratives of progress or conflict, these chapters emphasize the degree to which intention and outcome are separated by accidental confluences, redirected intentions, and unforeseen outcomes..."
In other words, the built environment is often unplanned in ways we don't normally acknowledge.
b. Discussions of styles or movements are complicated by the fact that they are defined by their 'minor' constituents. The "great" buildings, those which we naturally prefer to focus upon, are extraordinary in the sense that they usually flout the conventions of the style or movement. (Joan Ockman wrote about this in her article "Toward a Theory of Normative Architecture," 1997.)
c. Taken together, these points mean that style is practically the opposite of deterministic. It's more properly understood as a framework constructed after the fact.
d. Also, we're often not clear about period vs. style as different concepts.
e. Richard Longstreth's essay “The Problem With ‘Style’” (1984) has much to offer. One interpretation of Longstreth's point: "We miss out on a deeper understanding of the built environment when we endlessly categorize it." (link)
3. Interpreting buildings is both a scholarly and a non-scholarly activity.
a. Many of the important writers of the past that we admire---I'm thinking of people like Lewis Mumford, Esther McCoy, Ada Louise Huxtable---were not scholars. They freely mixed interpretations and facts, but they also had tremendous insights about buildings and people and trends. There is a tension in the discipline between a desire to write more freely and a need to maintain academic rigor.
b. Since journalism is the first rough draft of history, historians depend on critics and other non-scholarly writers. However, this is perilous, since: "The criteria by which architecture critics judge buildings are usually left unstated, slipping beneath the radar of even attentive readers: you must string together a series of articles to construct the underlying belief system." (Joseph Giovannini) Moreover, today's architectural criticism seems not to operate by the traditional ethics of journalism (cf. the Martin Filler-Zaha Hadid episode).
4. Other disciplinary boundaries are complicated.
a. The relationship between Architectural History and Historic Preservation is ill-defined. They are different activities with different skills and conventions, but with significant overlap. I think of AH as theoretical and universal, and HP as applied and local. It's a bit like Economics and Accounting; you may not want to ask an economist to do your accounting, and vice-versa.
b. The relationship between Architectural History and Vernacular Architecture Studies is also problematic. Everyone understands there to be a difference between "Architecture with a capital A" and "architecture with a lower-case a," but it's practically impossible to define or defend this distinction. Most scholars just choose one to the exclusion of the other. Dell Upton (quoted in the previous sentence, is the person who has worked most vigorously and successfully to transcend these boundaries and present a unified view of our built heritage.
5. In my opinion "The Canon" is a valid and valuable concept, although it's also limited by being self-perpetuating. Historians of my generation are always expanding The Canon or arguing against it. It's probably better to think about canonical buildings for specific issues, like: the Larkin Building is canonical in the history of air-conditioned architecture. But a general canon is still useful for introductory textbooks or surveys as the first platform on the scaffold of higher knowledge.
See also: The "flawed texture" of history