The notion of purity in the Torah is a very complex one. In Western Society we associate notions of purity with physical purity. Impure means “dirty”, pure means “clean”. But this is not how the Torah sees the idea. After all, in this week’s reading the agency of purity is the ashes of a red heifer and yet anyone involved in preparing them becomes impure. This doesn’t make sense.
Firstly, it must be said that the purity we are talking about is simply being in an appropriate state to participate in Temple ritual. In the ordinary way of things, most Jews would have carried on a perfectly normal existence throughout the year and across the world while being in a state of “ritual impurity”. This would have had no effect whatsoever on, say, the daily life of say a rabbi in Babylon or a rebbetzin in Rome or a Dayan in Worms. The fact is that most humans are in a state of ritual impurity all the time, and indeed at one stage the rabbis actually made a law to the effect that the soil of the Diaspora was ritually impure. (Louis Finkelstein argued that this was to protect the Israeli pottery industry! Reminds one of current commercial practices.)
It was only if one were a priest that this would be a daily problem, because you couldn’t eat tithes or other sanctified food in a state of impurity. But for the common and garden Israelite it was only relevant if you wanted to go and visit the Temple. Yes, three times a year there were mass pilgrimages, and tourism existed in those days too. So the real issue was not a negative one of suggesting that we were all dirty, but rather a positive one that suggested that if one wanted to elevate oneself, to go up to the Temple, then one had to go through a very serious process of preparation and purification. Perhaps “elevation” would have been a better word to use, but the effect is the same. The symbolism is what really counts.