[throwaway60707]

> Most authors don't even bother building in reasons why that can't happen, its just that no-one thinks of doing it.

Is it really necessary to spell out that a civilization capable of building a FTL starship is also capable of building a sufficient defensive technology?

> I daresay such a civ is not doing it for conquest, but to discover and explore. If the urge is militaristic, then such a civ would turn on itself long before the project succeeds.

I think this is much more complex. Consider a civilization so advanced that this is children's toys for them - and then that civilization falls. Then, on the scraps of it, a new imperialistic faction is built and they go for the conquest; they don't even need to understand the magic that powers their warships. I recommend you to read the full Foundation series in chronological order.

[aldarion]

"Is it really necessary to spell out that a civilization capable of building a FTL starship is also capable of building a sufficient defensive technology?"

We have had ICBMs for a long time, yet no sufficient defensive technology as of yet.

Beyond the fact that using them would lead to MAD, that is.

[javajosh]

I've read everything. I probably read the Foundation series before you were born (assuming you're 20-something). In fact, Asimov certainly knew that FTL was fraught - but he was writing for a living, and FTL was in vogue and he used the hyperspace version of it. It's unfortunate - I would have liked to see more grounded SF from him

[throwaway60707]

Well the issue remains the same with Bussard ramjets. It's just simpler to make so the whole scenario is more likely (though still very unlikely, ofc).

[FreshStart]

Kind of like tribalism on earth prevented empires?