Earlier quoted context omitted.
You've made some excellent points here, mate, thanks.
They are pretty weak points. By his logic, when you join a company and work you are speculating that you will get paid a salary. At that point everything is speculation and nothing is certain. By writing this comment I am speculating that a HTTP call will be made that results in a database entry. Since humans are not perfect and never have complete information about a system they engage in speculation in every single…
You've reduced his argument to ridiculousness. That's kind of low-effort, so in that spirit: It's true, nothing is in fact certain. Telling yourself otherwise is a convention that makes it easier to live and be resilient.