What is meant by the phrase in 1900 europeans believed the world was their oyster?

Excerpt from w. e. b. du bois jon reese 4 du bois was one of the first male civil rights leaders to recognize the problems of gender discrimination. he was among the first men to understand the unique problems of black women, and to value their contributions. he supported the women's suffrage movement and strove to integrate this mostly white struggle. he encouraged many black female writers, artists, poets, and novelists, featuring their works in his crisis magazine and sometimes providing personal financial assistance to them. the cause was that w. e.b. du bois encouraged many black female writers, artists, poets, and novelists. what was the result? think about cause-and-effect relationships.