Description: No variable is (effectively) free in a non-theorem. (Contributed by Mario Carneiro, 6-Dec-2016) df-nf changed. (Revised by Wolf Lammen, 12-Sep-2021)
| Ref | Expression | ||
|---|---|---|---|
| Hypothesis | nfnth.1 | |- -. ph |
|
| Assertion | nfnth | |- F/ x ph |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | nfnth.1 | |- -. ph |
|
| 2 | nfntht2 | |- ( A. x -. ph -> F/ x ph ) |
|
| 3 | 2 1 | mpg | |- F/ x ph |