Cause and Effect

"Newton found that gravity is the cause of falling of an apple."
Is it true?
Saying gravity is the cause of falling of an apple is not true. Gravity alone cannot make any apple to fall. Presence of a gravitational field does not guarantee that an apple would fall.
If a cause cannot  individually and consistently produce an effect, then the cause is not a cause of the effect at all.
Can we say gravity is a cause among many other causes? No. If occurrence of many number of causes guarantees an effect, then the world is a completely predictable place. If we assume that the world is not predictable, then an effect cannot have a single cause or many causes.
For example,

1. There is an apple tree.
2. There is at least one ripe apple on it.
3. A wind is rocking the branches.
4. The tree is in a gravitational field.
5. There is a ground beneath.
6. There is enough light to see.
7. There is a man to report the fall.
8. The man is honest.
9. He knows English.
10. All the above are true.

Even with all these apparent causes if you are not confident enough that an apple would fall, then you have some idea about the working of the world. None of these individually or collectively guarantee anything. In other words, they do not cause anything, including the fall of an apple. So the word 'cause' does not mean what we mean by that word.