The Three Lions head into the competition looking to make amends for a string of disappointments at major tournaments, most recently seeing them crash out of Euro 2016 to minnows Iceland at the last-16 stage.
Having also been floored at the group stage in Brazil four years ago, Southgate admits that simply making it to the knockout rounds will be a challenge over the next few weeks.
Ahead of his side's opening Group G clash against Tunisia in eight days' time, Southgate told reporters: "My job is to allow people to dream, to make the impossible seem possible. Why would I limit what they feel is possible?
"We are looking forward to going and I've said to them that we are going to attack the tournament. There is an optimism about youth. They believe anything is possible, which it is.
"None of us are going to get excited for just getting out of the group but we have got to play and prepare perfectly to get out of the group first."
England head into the World Cup finals with momentum on their side, as they have gone 10 games without defeat.