In the words of the fine litigators at The Good Wife's Lockhart/Gardner, let's stipulate that John D. MacDonald's "Susceptibility" is a deeply problematic work. The planet of the pioneer vixens is a weirdly troublesome image, even before we get to the fact that the entire story is predicated on Deen's lack of agency. All things considered, "Susceptibility" hasn't been collected or reprinted since 1978, and that feels about right.
However, "Susceptibility" does tackle several of the themes relevant to this week's "action hero" focus. (And, to be fairn, the book's terrible sexual politics are pretty on-theme as well.) These include the action hero both as a 'lifestyle choice' and as a means of guilt-free rebellion.
Sean Mallow lives in a delightfully Utopian future with everything free and comfortable and filled with joy. Yet still he is driven to live on the fringe of that society. As a Praecursor, he is someone that goes into relative (but not absolute) danger. Sean's clearly flung himself into his Praecursor task, he's even got the manual memorised. But, as Deen demonstrates, even that isn't enough for him. Ultimately, he chooses more - more danger, more risk, more work and more adventure. "Susceptibility" is set up as not as a conclusion, but as an origin story. His final decision is the moment where Sean Mallow decides to step outside the rules of society and devote himself to a more adventurous path.
"Susceptibility" is also an expression of John D. MacDonald's thinly-veiled derision for the rules or so called 'values' of society. Sean comes from a community that praises indolence and decadence as good and worthy. He, in the action hero mould, is disgusted by this and makes the right (narratively speaking) choice by resigning his role to live with Deen. This is the balance of guilt-free rebellion that characterises action/adventure characters. Sean is free from the rules and constraints of society, but he's doing so for the greater good - he can do what he wants, blamelessly.
Science fiction allows MacDonald a thematic conclusion that he was unable to reach in his Earth-bound stories. MacDonald's contempt for the lush life is present throughout all his works, but rarely does he have the opportunity to be this explicit about it. Travis McGee, for example, spends his entire life trying to escape the system but failing - as the series goes on McGee signs up for credit cards and sees his Florida coast devoured by condominiums and grow inexorably more tame.
As much as MacDonald disliked the changes he was seeing, he couldn't prevent them in real life, and had to accept them in his crime and literary fiction. In "Susceptibility", however, he has the freedom of science fiction. Even if Earth has fallen prey to civilisation, MacDonald can dream of a universe filled with pioneer planets, and give his adventure-seeking characters the wilderness they desire.
Image: James Vincent's original art for the story, from Galaxy, January 1951.