"If, then, archeology deals with the past, in what way does it differ from history?" Does it mean, if archeology deals with the past, then in what way does it differ from history? No. Not this, except that the diference is small. . If, then, usually means that this sentence IS the "then" caluse of something that has gone before. We must all assume that archeology deals with the past. If, then, it deals with the past, we should .... . Its assumed that it will rain Thursday. If, then, it's supposed to rain Thursday, we should take coats that day. .