Of course we often feel we are a lone voice, a lone witness. Yet insofar as we are salt the one grain which we are encourages another grain here to come forth and another grain there. It takes several grains to make a pinch. But it takes only one pinch to be effective. Centuries ago the prophet Elijah complained that he was the only salt-grain left in Israel.
Many grains make one pinch.
And one pinch is effective beyond our imaging. How effective he knows we can be is measured by his caution that our saltiness, yours and mine, we must ever retain, lest we cast away.