| The following are all equivalent. |
| A implies B |
modens ponens |
| B if A |
(top down) |
| (not B) or A |
|
| (not B) implies (not A) |
modens tollens |
| A or (not B) |
|
|
 |
The two tables are
symmetric. Which one is
true? The other one is then
false.
If the above are
true, then the following are
not true or
false.
| The following are all equivalent. |
| B implies A |
converse error |
| A if B |
(top down) |
| (not A) or B |
|
| (not A) implies (not B) |
fact check fallacy |
| B or (not A) |
|
|
 |
There are a terrible lot of lies going about the world, and the worst of it is that half of them are true. Winston Churchill.
Note that if the bottom table is
true, then the top table is
not true or
false. To see this requires algebraic substitution of names for other names (as in a code). This is part of the programming process in computer science, software engineering, etc.
Matthew 24:22 And except those days should be shortened, there should no flesh be saved: but for the elect's sake those days shall be shortened. [kjv]
και ει μη εκολοβωθησαν αι ημεραι εκειναι ουκ αν εσωθη πασα σαρξ δια δε τους εκλεκτους κολοβωθησονται αι ημεραι εκειναι [gnt]
Matthew 24:22 And except those days should be shortened, there should no flesh be saved: but for the elect's sake those days shall be shortened. [kjv]
