However, it’s fairly easy to see that this isn’t necessarily the case with a conditional statement. Consider the following statement
“If we go fishing, we’ll catch fish.”Such a statement need not be taken as prescriptive (never mind that it’s awfully optimistic). That statement is merely a truth claim. There is a protasis and an apodosis, but an actual command to go fishing is conspicuously absent. It’s merely stating that if we go fishing, we’ll catch fish. Maybe we’ll go fishing and maybe we won’t… but if we do, we’ll catch fish. If catching fish is something to be desired, then we’ll be inclined to go. If catching fish is undesirable, then we’ll be inclined not to go.
On that basis alone, we should be cautious about how we read conditional statements.
In the case of 1 John 1:6-10, the reader will be more inclined to take these as prescriptive if he’s convinced that those collective pronouns refer to believers. But when we consider the possibility that these collective pronouns refer to humans generally, these conditional statements lose whatever prescriptive feel they may have had. Now John can be seen to be simply telling it like it is. These conditional statements become mere descriptions of reality, and as mere descriptions of reality, it’s entirely reasonable that John would be describing this reality to believers, in just the same way that one believer could say to a group of believers “He who believes in Christ has eternal life.”