When you think about inspiring advocates and campaigners, you often think of their powerful words.
Decades later for example, millions of people continue to be moved by Martin Luther King's I Have A Dream speech.
Words have an incredible ability to stir up emotion - and to get people taking positive action.
The vegan movement is currently seeing something of a surge - and for many new advocates, it was a powerful speech that made them get involved.
Here are five amazing speeches that moved people to make real change.
1. James Aspey - This Speech Is Your Wake-Up Call
Aspey has the very powerful combination of passion and charisma.
His low-key delivery - with his deeply moving words - means people are drawn to listening to him.
Perhaps this explains why so many millions of people have watched his famous speech.
Aspey promotes a very accessible, attractive style of effective advocacy - and he is opening hearts and minds worldwide with his words.
2. Gary Yourofsky - Best Speech You Will Ever Hear
A controversial character for some, Yourofsy's 'best speech ever' has been credited with turning a massive eight percent of the Israeli population vegan, and more people globally with millions of views on YouTube.
While people ask valid questions about the now-retired activist's use of language, and comparison of human atrocities with animal atrocities, the sheer number of people who have been inspired by the speech means it makes this list.
As one convert says: "I ate animals before I watched it, but afterwards I had no arguments."
These are certainly discussions that could be, and are being, had around his tactics.
Yourofsky doesn't pull any punches, asking questions like: "I'm curious - if you think there's such a thing as humane slaughter, do you think there is such a thing as 'humane rape'?"
3. Dr. Melanie Joy - Toward Rational, Authentic Food Choices (Tedx talk)
Renowned Harvard-educated professor Dr. Melanie Joy has inspired millions worldwide as the author of Why We Love Dogs, Eat Pigs, and Wear Cows.
Her work coining the concept of carnism, and spreading its message, has been a huge breakthrough in how millions of people view the use and exploitation of animals.
Dr. Joy's brand of effective advocacy appeals to a huge range of people whose minds have been open to her critical way of thinking.
As one viewer says: "I was a meat eater... until I saw this video.
"Now my perspective has changed so much.
I feel so bad for eating animals."
4. Bite Size Vegan - This Speech Will Change How You See Everything
Bite Size Vegan - aka Emily Moran Barwick - creates short videos which are designed to be as informative as possible, while still being fun.
At 30 minutes long, this video (which Gary Yourofsky has called 'excellent') is a little more than bite size, but Barwick's managed to pack it with facts.
She says: "This speech will change how you see everything. Learn the impact your individual choices have on the world around you and how simple actions can heal the planet, humanity, and other beings.
"If you’re concerned about the state of our world, if you love animals, if you care about the environment, if you want to be healthy, and if you want to feed the world’s hungry, open your mind and heart and listen."
5. Philip Wollen - Animals Should Be Off The Menu
This speech shows Australian philanthropist Philip Wollen addressing the St. James Ethics and the Wheeler Centre debate.
The Vice-President of Citibank has become a vegan and animal rights activist since leaving his exceptionally successful career in the financial sector. He also works with the homeless and terminally ill.
This speech (which offers subtitles in 18 languages) isn't long at just 10 minutes, but it packs a punch.
Wollen is a persuasive speaker and outlines the ethics behind eating animals.
As one viewer says: "Wow... I have been a vegetarian and now I am going to be a vegan and will spread the words.
"Thanks to Sir Phillip Wollen. Your speech will touch billions of heart."