> - the speed with which tools like von Neumann probes could proliferate the galaxy
> - the likelihood that somebody somewhere over millions of years would create a von Neumann probe (computer viruses didn't take long to make)
The problem with this is no one has demonstrated any technology that can be used to make a von Neumann probe, and if you look at it from an engineering perspective, it's not clear that it's feasible at all. We are nowhere close to building machines that can build machines, much less ones that can do so when the inputs are "mine this rock", much less ones that can identify the rocks to be so mined, much less ones that are capable of being launched onto another planet, much less ones that can land on exoplanets, much less ones that can identify said exoplanets, much less ones that can remain in good working order for the entire journey.
That's... a lot of steps that need to be met for a von Neumann probe to be possible in the first place, almost none of which are demonstrable anytime soon. Should any one of those things be impossible, or merely impracticable, then that means von Neumann probes themselves are so. Until it's demonstrated that there's a good reason to think that von Neumann probes should be possible to construct, I don't think it's reasonable to argue that we should assume they already exist.
> - the likelihood that somebody somewhere over millions of years would create a von Neumann probe (computer viruses didn't take long to make)
The problem with this is no one has demonstrated any technology that can be used to make a von Neumann probe, and if you look at it from an engineering perspective, it's not clear that it's feasible at all. We are nowhere close to building machines that can build machines, much less ones that can do so when the inputs are "mine this rock", much less ones that can identify the rocks to be so mined, much less ones that are capable of being launched onto another planet, much less ones that can land on exoplanets, much less ones that can identify said exoplanets, much less ones that can remain in good working order for the entire journey.
That's... a lot of steps that need to be met for a von Neumann probe to be possible in the first place, almost none of which are demonstrable anytime soon. Should any one of those things be impossible, or merely impracticable, then that means von Neumann probes themselves are so. Until it's demonstrated that there's a good reason to think that von Neumann probes should be possible to construct, I don't think it's reasonable to argue that we should assume they already exist.