Viewers not already interested in historical Asian art may care little for such discriminations and consider the exhibition as a whole too academic. But the earmarks of regional and period styles give us our bearings when we confront artifacts of times and places remote from our own.
We simply see more articulately when, confronted with a historical object, we can make an educated guess whether it originated in, say, China, Tibet or Sri Lanka, and roughly when. That exercise has more than academic or amaze- your-friends value: It enriches our capacity to see and so helps to take us outside ourselves.
For example, classic Sri Lankan Buddha images, like some in "The Kingdom of Siam," incorporate an element that suggests a headdress. It depicts the "flame of enlightenment" emanating from the crown of the Buddha's head.
Other features of Sinhalese sculpture include pleated, layered drapery, much heavier than anything seen in corresponding Indian images, and a half rather than full lotus position of the feet in seated Buddha figures.
At a certain point in the history of Sri Lankan Buddhism, a prohibition on hollow images of the Enlightened One came into force, making much Sri Lankan metal sculpture recognizable (though not to mere viewers) by its exceptional weight as well as by stylistic clues.
"Guardians of the Flame" contains enough anomalies, works in timeworn condition and variant styles to remind us of the difficulty of expertise in such a field.
Visitors familiar with Buddhist art will notice an unusual mudra, or symbolic hand gesture, in a couple of pieces on view. It appears in monumental stone images of a standing Buddha at Avukana, considered prototypes of later style, and is unique to Sri Lankan art.
In the traditional mudra of quelling fear, the Buddha holds his right hand up, about shoulder level, palm out. In the Sri Lankan examples, the palm is rotated a half-turn inward.
Asked about the origin of this seemingly slight but distinctive variant, Cantor Center Asian art curator John Listopad knew of no solid explanation. Nor is a variant meaning associated with the iconographic departure. He speculated that it might even have originated as a master carver's solution to an anomaly in the stone precluding execution of the conventional form. Despite how well scholars understand certain features of Sri Lankan antiquities, mysteries remain.
In addition to sculpture, "Guardian of the Flame" includes Buddhist palm leaf manuscripts and lacquered, decorated manuscript covers of arresting aesthetic force.
Throughout much of Sri Lanka's intermittently turbulent history, the visual arts benefited by reciprocal support between rulers and the Buddhist establishment. After 1815, British occupation of Sri Lanka brought that long cultural symbiosis to an end.
Like every exhibition of its kind, "Guardian of the Flame" confronts most visitors with a peculiar feature of our own cultural situation: In place of these artifacts' intended uses for restitution of belief, we have mere aesthetic reception and perhaps academic study.
An exhibition such as this encourages reflection on how limited a mode of engagement even the most informed aesthetic response is likely to be.
Guardian of the Flame: The Art of Sri Lanka: Sculpture, manuscripts and manuscript covers. Through June 12. Cantor Arts Center, Stanford University, Stanford. (650) 723-4177, www.stanford.edu/dept/ccva.