What Empedocles thought was that basic objects consist of water, fire, earth, and air. Also, he thought the specific outcomes depended on the different combinations of each. He went on to say that particles of these objects do not change, but the "objects of experience" do change. These ideas are compelling to me because they are still used in physics today.
Another thought of Empedocles was that changes occur because of "love and strife", or in other words because of attraction and repulsion or good and bad. A practical example would be taking the four examples of water, fire, earth, and air, and looking at them like they were dry ingredients in a cake. Love and strife are oil and water. When mixed together well, it blends smoothly, but if left alone, separation can happen. An additional example would be yin and yang.