«كل إنسان ضاحك بالفعل»
Every human is actually laughing, in the example’s stated sense.
The text also supplies a negative counterpart. These illustrate the technical role of bi-l-fiʿl; opposite formulations are not to be accepted as simultaneously true of the same subject in the same respect and at the same time.
“This door is open now” is an assertion about actuality. It does not establish that the door was always open, will always remain open, or had to be open. One must not import necessity or permanence into a generally absolute judgment merely because it affirms or denies something.