Senegal's most powerful men are not politicians, but the leaders of the country's Islamic Sufi brotherhoods, to which a very large proportion of Senegalese belong, and whose influence pervades every aspect of Senegalese life.
Everywhere you go in Senegal, you see the same picture: An old black and white photograph of a figure dressed in white, a long white scarf wrapped around his head.
It's the only existing picture of a man called Cheikh Amadou Bamba, the founder of the Mourrides, Senegal's richest and most powerful Islamic brotherhood.
You don't have to be in Dakar for long to realise that if everyone who displays his picture is a member, this is a very large organisation indeed.
Its ties bind every Mourride to every other, but one of the strongest ties of all is the one which binds a Mourride to his spiritual guide and teacher, his Marabout or Cheikh.
In a personnel consultant in everyday life, is a devout Mourride and a descendant of the movement's founder.
He remembers the day he met his Cheikh as vividly as others remember falling in love.
"It was in Thies," he says. "On a Monday I think. We met, we become friends. He asked after me, said, "Massamba, you must come, you must take tea, eat with us.
"I was looking for just this kind of man. He bowled me over, seduced me if you like, and I became his disciple."
The relationship, he says, is for life, and is more important and intense than any relationship with a woman.
The Cheikh can bring spiritual comfort and open a path to God. But he can also, according to Massamba Lo, help with more practical affairs.
If you are thinking of starting a business, for instance, he can give the enterprise his blessing.
But these Cheikhs are very well connected. He can also put you in touch fellow Mourrides who might be able to offer a helping hand.
For people like Massamba Lo, Mourridism supplies spiritual nourishment, business networking opportunities, a social security system and a fulfilling social life - all at the same time.
Disciples of the same Cheikh meet for special days of celebration, with prayer and devotional music, and the collection of gifts for distribution to the poor.
Mourridism, says Massamba Lo, isn't simply a large part of his life - it is his life itself, the way he orders his existence.
The Cheikhs are in a position of power, but also of responsibility.
"Their main job is to educate people in the religion, but they have also a social responsibility because they have to make them work," Hadim Mbacke, himself a renowned teacher and scholar, told me.
"They have to marry people who need to be married, they have to reconcile people, they have to help people to get good health care and many other things."
All this takes resources, but the Mourrides are rich. Hard work is part of their creed. Their founder, Cheikh Amadou Bamba, placed great emphasis on the Prophet Mohammed's saying: "Work as if you were going to live forever, and pray as if you were going to die tomorrow."
And they work, not just for themselves but for the brotherhood. Some disciples contribute their labour on their Cheikhs' farms; others bring cash.
"You have rich disciples and poor disciples, says Hadim Mbacke. "You have people who work in the government - the president, the ministers - all these people bring you a lot of money.
"Some people bring you perhaps $10, others even $1m sometimes, so he takes from the rich and gives to the poor."
For members of the brotherhood, Mourridism is all pervasive; for Senegal it's a whole parallel structure, hidden beneath the surface of national life.