One ancient theory was an idea called vitalism, which claimed that living things were unique because they were filled with a special substance, or energy, that was the essence of life.
Terdapat satu teori kuno bernama vitalisme, yang menyatakan bahwa makhluk hidup itu unik karena mereka diisi oleh suatu zat khusus, atau energi, yang merupakan intisari kehidupan.