But where does this actually work? We also believe we can safely trust someone who has already told us their secrets. We think: this person would never betray our secrets because they'd be afraid we might betray theirs. This is how careless people get trapped by soldiers in Rome. A soldier sits next to you in regular clothes and starts badmouthing Caesar. You think his criticism proves he's trustworthy. So you also say what you really think. Then you get dragged away in chains.
where is this done? Besides, we have also this opinion that we can safely trust him who has already told us his own affairs; for the notion rises in our mind that this man could never divulge our affairs because he would be cautious that we also should not divulge his. In this way also the incautious are caught by the soldiers at Rome. A soldier sits by you in a common dress and begins to speak ill of Cæsar; then you, as if you had received a pledge of his fidelity by his having begun the abuse, utter yourself also what you think, and then you are carried off in chains.