There are some things in life I don't understand. Applied mathematics. Bunions. The working class persistantly voting conservative. Frank Borzage languishing in critical limbo. What is wrong with you people (I mean critics, not you, dear reader)? It can't be because he made silly women's pictures, because Ophuls, Murnau, Sirk and Minnelli have all appeared in Top 100 lists in the last two decades. I don't get it: Borzage was definitely a master: of light, space, plot, critique and emotion. His films - of which I have only seen four, not for want of trying - are among the most emotionally intense and beautiful things in cinema. They offer the straightforward weepie thrills we expect from melodrama, as well as an unexpected critical dimension.

Although I just about prefer the faded self-pity of THREE COMRADES, SEVENTH HEAVEN is probably his masterpiece. It is astonishing in so many ways: let me list some. The more I see of her, the more remarkable an actress I find Janet Gaynor. The film's progressive politics - an impoverished victim, suicidal, prostituted, heinously whipped by her sister, transforms into a loving wife, fierce protector of her home, member of the workforce, and eventual carer of her husband - owes much to her all-encompassing performance.

The use of light and shade to represent the emotional life of the characters. The (Americanised) Expressionistic use of space, which breaks up conventional point of view to provide varying levels of experience and ways of looking. The deceptively delicate poetry of the imagery. The tacit outrage at a system that forces people to live so badly. Even the movie score, uniquely, shows an intelligent perception of what Borzage was trying to do.

Diane and Chico have many obstacles thrown in their way, both individually and collectively, but the most terrifying and inexorable is that of the war. It is quite shocking to find a melodrama - by its nature domestic, local, specific, small-scale and personal - erupt into a war film, that most national of crises. The effect is wrenching, but no more so than the events of the melodrama which alternated the most radiant highs with the most despairing lows. Witness the astonishing, jerking, tracking shot as Diane flees her sister, shattering the smooth rhythm of composition and editing.

Borzage, like no other director before Kubrick, is responsive to the farce of war, as well as its horror. There are sublime scenes of comedy amidst the carnage. The battle scenes put pretenders like ALL QUIET ON THE WESTERN FRONT to shame; the sheer scale and irrationality of war bursts the screen. Points of identification become lost, the tyranny of destruction is a perversely beautiful thing.

It is in this context that the couple's transcendent love must be seen. What could have been as a desperately mushy romance with its talk of the Bon Dieu and heaven, becomes a necessary rebellion, a refusal to succumb to social pressures, war, nation's follies, domestic horrors, betrayal or death. So the ending is not preposterous, but the perfectly comprehensible hallucination of a woman who, having been raised from hell, could not possibly leave heaven now. Imperishable.