THE EVIDENCE is mounting, but proof remains a nebulous thing.
Nick Foles progressed Thursday night.
In the Bengals' 34-13 rout mottled by five turnovers and a blocked punt, there were reasons to like the Eagles' third-round rookie a little bit more.
He hit seven receivers with 16 passes on 33 attempts for 182 yards and a touchdown.
He led an undermanned offense back from a 10-0 first-quarter deficit to a 13-10 halftime lead.
He endured nine penalties.
He weathered wave after wave of ravenous rushers, and was sacked just once.
He operated without the safety net of a running back; Bryce Brown, suddenly wary of the middle of the field, avoided holes and managed 34 yards on 16 carries.
All of this, Foles transcended.
For Andy Reid and the Eagles, that's good news, and bad news.
Good news for the Eagles. They might have stolen a franchise quarterback in the third round.
Bad news for Reid.
If Foles can operate efficiently as a rookie in his fifth start with a cast of six other backups against a playoff-caliber team like the Bengals, certainly he can adapt to a new coaching staff.
Foles' success in this moment makes Reid and Co. expendable.
Reid's quarterback mafia includes offensive coordinator Marty Mornhinweg, credited with reconstructing flawed veteran Michael Vick's skill set, and quarterbacks coach Doug Pederson, whose riveted pupil Foles has been.
Perhaps Pederson could be asked to stay. He always has been popular here.
In the afterglow of Thursday night's turnover horror show, the level of Foles' talents and the depth of his skills hardly seem relevant.
In the afterglow of every game since Foles took a snap 51/2 weeks ago, the level of his talents and the depth of his skills has been the only things that are relevant.
Be careful what you blame him for Thursday night.
Remember that he helped turn a 10-0 deficit midway through the first period into a 13-10 halftime lead.
He cannot be blamed for the four consecutive turnovers in the second half.
Well, the first one, maybe: But, to be fair, Foles threw it as far as he can.
Foles didn't call the play, the 40-yard bomb that Leon Hall easily intercepted.
It was Foles' first interception since his first start.
It will not be his last.
There could have been a half-dozen others Thursday night, and about 15 all told this season.
Reid blames mechanics more than arm strength.
"He's got a real strong arm. I'll put his arm up against anybody in this league," Reid said. "He's got to get his feet around...Get enough body and legs into the throw."
Can he make the throw?
"I can," Foles promised. "Yes."
But still. All of those near-interceptions... But there haven't been. So there.
Anyway, from now on, only 35-yard bomb plays. Maybe 30-yarders.
Foles cannot be blamed for the disconcerting signals the field-goal blocking unit used that turned a probable field goal into an actual touchdown early in the fourth quarter.
In fact, on a night when Reid's firing never was more justifiable, when the Eagles never looked worse as a franchise, Foles stood tall, above the fray.
Yes, he continued to underthrow receivers, even ones within his limited long-ball range.
His 46-yarder to Jeremy Maclin in the second quarter was about 10 yards short of where it needed to be. Maclin had to wait for it.
He missed Maclin with a 40-yarder early in the fourth, too, another near-interception.
There would be no comeback from 11 points down, the way he led them in Tampa on Sunday. That's the stuff of legend.
Legends often need addendums.
For one thing, the Eagles were 21 points down Thursday night.
For another, the Bengals brought in a top-10 pass defense. The Bucs' is the worst in the NFL.
Nevertheless, there were signs of continued improvement.
He recognized the occasional blitz and generally avoided it. He exited the game un-concussed, unsprained, undislocated.
He took an intentional-grounding penalty, but there were receivers within 20 yards of the ball. It was a thought.
Foles didn't always have his playcallers on his side, either. Really; that pass to the backup center in the end zone had no chance of succeeding.
But, with a backup tight end running the starter's routes, with no burner on the outside and with a patchwork line acting as dike vs. a sea of powerful pass rushers, Foles did fine.
He has a swashbuckling insouciance, a reckless manner that lets him flip an improvised shovel pass to startled fullback Stanley Havili. So surprised was Havili that he strained his hamstring.
Not surprisingly, Foles has an affinity for the middle of the field. That's where he found Riley Cooper for their touchdown.
He has a phobia for the sideline, where mechanics and arm strength are everything. Given the geometry of football, those throws are, by definition, longer and harder to make.
He's getting there.