[Broken_Hippo]

These aren't indicators of lack of trust, merely that things happen.

Even with testing, not all STD's show up on tests - this is why folks get tested regularly. Many folks won't know they have an STD (think HPV). Condoms break, get forgotten, and so on. People do stuff when they are drunk.

Rape happens (rape isn't a lack of trust but rather something else entirely).

[Loq]

   These aren't indicators 
   of lack of trust

I disagree. There are multiple levels of trust:

- Your partner that they don't lie about taking contraception, that they have taken it as required.

- The medical sciences and medical regulatory authorities that the contraception works as expected.

- Pharmacist that they don't sell counterfeit medicine

and many others. Society is largely based on trust.

[Broken_Hippo]

But trust doesn't mean you won't have demand for plan B. It doesn't mean you won't have STD's. Society is, indeed, based on trust but yet, none of these products means you don't have trust.

Humans happen and make mistakes. Condoms break. Therefore, plan B.

One doesn't have to be promiscuous or untrustworthy to have an STD. All that means is that you've had sex with someone. Someone might not even know they have an STD either. Even if folks have more than one partner, it doesn't actually mean they are sleeping around or that they are being dishonest, nor does it mean they'll get an STD.

In addition, if you are trusting that your partner has taken something as required, you probably are in a sexual relationship with someone you are familiar with. Otherwise, the prudent thing would be to use a condom and hope it does not break.

Contraception working as expected leaves a lot of room for error. Again, condoms break. Medications interfere with hormonal birth control and most folks don't take it like laboratory settings, which increases risk of pregnancy. This is all still "working as expected".

[YorkshireSeason]

What you say is true, but I'm not sure it's in contradiction with my point.

[emiliobumachar]

If The System tells me that contraceptions are X% effective, and I believe them, and it's true, the problem remains of the failure rate. That's unrelated to trust.

[YorkshireSeason]

That's maybe mostly a semantic quibble about the precise meaning of trust. I don't think it's considered absurd to say "I trust that my plane won't crash" when flying. Maybe it's more usual to say "I hope that my plane won't crash". It appears to be the case that we "hope" if we don't see the social dimension of the phenomenon we are referring to, while "trust" is also communicates a stronger social dimension.

Note also that in interactions with humans, we generally don't have a precise probabilities.

[rmellow]

Condoms break, despite whatever trust I have in them. That's when it's time for Plan B.