Wahab Riaz celebrates the wicket of England's Chris Woakes during the match on Monday. Reuters
The notoriously unpredictable Pakistan side held their nerve to beat the hosts by 14 runs at Trent Bridge on Monday, just three days after crashing to a seven-wicket defeat against the West Indies at the same venue.
That ended a sequence of 11 consecutive defeats in completed one-day internationals.
Arthur praised his team's resolve after a "shocking" defeat in their tournament opener.
"It was just so good to see us go out and play with the belief and intensity that we had spoken about," Arthur told AFP.
"When we put all three disciplines together we know we can beat anybody. We now need to stay consistent and ruthless."
Pakistan posted an impressive 348-8 against a potent England bowling attack, with fifties from veteran Mohammad Hafeez, Babar Azam and Sarfaraz Ahmed.
Pacemen Wahab Riaz and Mohammad Amir, and leg-spinner Shadab Khan, took the wickets to restrict England to 334-9 in their 50 overs.
"You could see the hunger, the determination and the resolve to do well in batting after a horror show and then the bowlers fought hard, so we need to repeat that in the coming matches as well," said Arthur.
Pakistan have won all seven of their World Cup matches against Sri Lanka dating back to the first tournament in 1975.
Pakistan will be tempted to bring in fast bowler Mohammad Hasnain for his raw pace, something that New Zealand exploited against Sri Lanka during their 10-wicket rout of their opponents in Cardiff on Saturday.
On Tuesday, Sri Lanka beat Afghanistan in a rain-shortened match, also in Cardiff, to breathe life into their campaign.
But the 1996 champions will be wary of another middle-order batting collapse after they lost five wickets for 14 runs against New Zealand and seven wickets for 36 runs against Afghanistan.
Sri Lankan coach Chandika Hathurusingha said he had told his batsmen to up their game.
"I don't give pep talks. I give honest talk, that's all.
"I tell them what has to be done. They have to come and perform," said Hathurusingha, who praised opener Kusal Perera for his 78-run knock, which helped Sri Lanka reach 201 against Afghanistan.
"He's an amazing player," said Hathurusingha. "We have given him the full licence to bat the way he wants to bat. We know that when he's come up, most of the time it's match-winning."
But one factor outside anybody's control is the weather, with persistent rain forecast for Bristol on Friday.
It is the first match at the World Cup in England and Wales to be abandoned without a result.
Sri Lanka started the tournament as rank outsiders and finished sixth of the nine teams, registering one of their three wins against the world's top-ranked one-day international side and hosts England.
Sarfaraz Ahmed's side needed to smash the world record for margin of victory in a one-day international but, after winning the toss at Lord's, they failed to muster enough runs to give them a chance.
Bangladesh must be all out for seven or lower if Pakistan are to deny New Zealand a place in the semi-finals alongside Australia, India and England.
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