Gareth Bale had given the hosts a lead with a precise free-kick but then their deficiencies highlighted this season surfaced again.
Tottenham failed to close out the game and Manu Adebayor headed in from a set-piece before sealing the win after Cesc Fabregas had edged Wenger's side ahead.
"It shows our spirit and belief and I was very happy with our game and our mental strength and togetherness. We have showed them all again," said boss Wenger.
Spurs were meant to be the team who could edge them out of the top four, but the lunchtime win at their rivals' took Arsenal top.
"Having lost Thierry (Henry), it has helped the belief and mental strength of the team to start well," Wenger added. "We never forget Thierry but we know that the team is blossoming and growing. There is something in the side: quality, of course, but also mental strength.
"I hope the good form continues. At half-time I could not complain because all we did wrong was not to take our chances. I felt that if we kept the pace high, we would have a good chance of winning."