"No," said Dumbledore instantly, when Snape asked.
"Professor, you don't understand. I'll do anything," he said, through gritted teeth.
"I think I'll make a good addition to the Order…"
"That's not the matter, Severus. You're a brilliant wizard, I'm aware. It's a matter of trust, and I'm not sure that I trust you," said Dumbledore.
"I can brew a potion… one that will force me to speak the truth. Then you'll have to believe me." Snape hated to beg. He could hardly recognize his own voice when groveled.
"Very well."
Snape had a feeling that Dumbledore had already thought of this solution, but wanted to here him sound desperate before agreeing.
Then, confirming Snape's suspicion, Dumbledore pulled a vile of honesty potion out from his desk.
Snape came forward and took a seat before the headmaster and then he took the vile. The potion tasted cold and bitter when he drank it.
"Do you want to be a member of The Order of The Phoenix?" asked Dumbledore.
"Yes," said Snape.
"And if I were to emit you, would you be completely loyal to me?"
"… Yes."
"Would you lie to Voldemort on my demand?"
"Yes."
"How do you intend on doing this?"
"Occumency. I'm very skilled at it, Professor."
"Okay, Severus. You can join the Order."
Snape felt relief and even happiness, but his face stayed still as stone.
"I presume I'm the only one who knows about this ambition of yours?" asked Dumbledore.
"No."
"Someone else knows?"
"Yes."
"Who?"
"Lily Evans."
"You told this to Lily Potter?" asked Dumbledore.
"Yes."
"Why?"
"Because it'd make her happy."
"And you want to make her happy because…"
"because I love her," said Snape.
"I see," said Dumbledore.
Snape left shortly after. He had achieved what he set out to do.
Severus Snape. Man. Wizard. Death Eater and member of the Order.