[PRL] Bob Harper's new blog

[Matthias Felleisen]

On Mar 17, 2011, at 11:26 AM, Dave Herman wrote:

> David's point about heated assertions without evidence is germane. Maybe you're trying to let the irony of refuting a blog post about the difference between booleans and propositions by asserting its falsehood without proof somehow be the proof itself, but I'm afraid even after 8 (count 'em) years of studying PL theory, my brain doesn't go that meta.
> 
> So for us mortals... care to explain?


That one is easy to explain and resolve. 

Plain 'true' is a value in the carrier of some model. 

Something such as 'Dave is at the other coast' is an assertion, which belongs to a completely different category than values. 

In classical logic, you reify 'true' as a simple proposition and then you can write 'Dave is at the other coast' ≡ true 

In others logics, you can't necessarily do so.