How many historic figures made positive impacts because they answered God’s call? Perhaps a call they’d heard during a mysterious experience such as having a vision or dream or hearing a voice?

We might never know for sure. But Florence Nightingale (1820–1910), also known as the mother of modern nursing, was definitely one of them. Her revolutionary practices saved countless lives and paved the way for other women to pursue medicine.

And it might not have happened had Florence not heeded God’s call.

Florence came from a well-off English family, with a learned dilettante of a father and a socially ambitious mother. No one had to work for a living. They were free to read, to ride, to entertain and to travel.

From the start, Florence’s native intelligence shone. She read voraciously, learned several foreign languages and had a good head for numbers, noting as early as age seven what dose of a certain popular medicine people should take: “16 grains for an old woman, 11 for a young woman and 7 for a child.”

Florence was an empathetic caretaker from a young age, nursing the ill back to health, beginning with four-legged creatures. When a nest of newborn mice was discovered in a mattress, 12-year-old Florence came to the rescue, feeding them with drops of milk and keeping them warm by the fire. Florence sprang into action once again when a sheepdog named Cap was attacked by ruffians and injured so badly it couldn’t put weight on its leg. Had Florence not offered to heal the dog’s injury with a warm compress and a bandage, the dog’s owner, a shepherd, would have had no choice but to put down the poor animal—it would’ve been a drain on his meager income.

Even back then, she boiled the water before using it to soak the bandage, ridding it of germs—decades before anyone knew what germs were or how they spread. Was it a penchant for cleanliness or a mystical prescience? However you look at it, Florence Nightingale was ahead of her time.

It’s easy to read stories like these about her life and think, Of course, she’s going to become a nurse. It was destiny. What else would she have done? There’s account after account of her dashing off to care for some ailing relative or injured creature. Yet the circumstances into which she was born made it highly unlikely. It was considered unseemly for a woman of her stature to work—let alone in such a disreputable profession as nursing.

According to the mores of Victorian England, Florence would forgo a career, marry a suitable husband, settle in a country house somewhere and produce a large batch of children. She might very well have done so—if not for God’s intervention.

On February 7, 1837, before she was to be presented to society as a debutante, Florence heard God speak to her. The day that changed the course of her life has been marked in history. The key word that she heard that day from God was service. She knew she was called to serve.

Florence was conflicted. If this were indeed God’s calling, wasn’t she also called to obey her father and mother? She found herself caught in one of those guilt-inducing struggles that give a bad name to the Victorian era, torturing herself miserably at times. An opportunity for service would open, she would be eager to follow it—after all, wasn’t it God’s will?—only to face fierce opposition from her mother, provoking dreadful scenes.

It became easier to avoid disappointing her mother and instead just say no to all of the suitors who came calling instead. By all accounts—and early photos—Florence was beautiful, charming and quick. Men did come, flirting, pursuing and even boldly asking, “Will you marry me?” No, she said. Adamantly, no. Her heart was already claimed by God’s call to service.

Over the years, however, socializing in Victorian society paid off. She made some important friendships. Among her dearest friends was Sidney Herbert, a bright, passionate politician. He was Secretary at War in 1854, when England was caught in the Crimean War. The British were fighting the Russian Army on the Crimean peninsula, and a shocking number of soldiers were dying in barrack hospitals. Perhaps Florence could help.

By then, in that era, she would have been considered an old maid, 34 years of age and unmarried. Still, God had been insistent in his call, once telling her during a trip to Egypt to “do good for him alone without the reputation.” Perhaps for want of people to nurse, she’d rescued other animals, including an owl she named Athena and kept in her pocket. She even took it to Germany, leaving Athena with her sister Parthe while Florence studied nursing there. She had pursued her calling against all odds.

In 1853, she’d been given charge of what we would think of as a private clinic. It was situated on London’s fabled Harley Street, known for its doctors. But Florence had no ambition to be a doctor, only a nurse.

At Herbert’s request, she gathered a coterie of other nurses and went to Turkey, where the injured soldiers had been transported. There her reputation was burnished. She became famous as the Lady With the Lamp, going from bed to bed, nursing the wounded soldiers into the late hours.

She discovered the soldiers had been dying in droves from preventable ailments. Linens had gone unchanged, meals unserved. Chamber pots overflowed, and the hospital was filthy, resembling more a putrid charnel house than a place of healing. Florence immediately created a basic standard of care. Using some of her own funds, she bought supplies, established practices of sanitation and dealt with a military bureaucracy that opposed her at every turn, hoping she’d go away.

Along the way, Florence continued to be touched by mystical experiences. In Turkey during the war, she had a vision of her beloved pet owl, who’d died shortly before she left England. She was walking home from the hospital one night “when Athena came along the cliff quite to my feet, rose upon her tiptoes, bowed several times, made her long melancholy cry and fled away.” Far from home and up against incredible odds, Florence found the vision was a great comfort to her. It was a reassurance that she was still on her God-given path.

Florence stayed in Turkey through the end of the war, remaining until the last wounded man left. Then, avoiding any furor, she made her way secretly back to England, as though to reaffirm that what she had done was for God alone.

Upon her return, Florence plummeted into depression and nearly died. She was understandably exhausted from undertaking such a long stretch of 18- to 20-hour days. She was also suffering from a mysterious illness that historians have only recently diagnosed as severe chronic brucellosis, which comes from drinking infected goat or sheep’s milk. The water in Turkey would have been undrinkable, and Florence wouldn’t have turned to beer, wine or spirits as most of the other doctors and nurses did. (Drunkenness was a serious issue for some of them.)

For the next 52 years, she lived in England as a recluse, but her work was far from over. In fact, you could say that her greatest impact came during this time. She spent her days haranguing the powers that be with letters and tracts, prompting them to set new standards of medical care that we have come to expect as normal: clean beds, clean sheets, clean rooms and caring nurses.

Florence died at the age of 90, after saving countless lives and changing the world for the better. She’d done what she’d been meant to do. She’d heard God’s call—and answered it.