“From the beginning nature has assigned to every type of creature the tendency to preserve itself, its life and body, and to reject anything that seems likely to harm them, seeking and procuring everything necessary for life, such as nourishment, shelter and so on. Common to all animals is the impulse to unite for the purpose of procreation, and a certain care for those that are born. The great difference between man and beast, however, is this: the latter adapts itself only in responding to the senses, and only to something that is present and at hand, scarcely aware of the past or future. Man, however, is a sharer in reason; this enables him to perceive consequences, to comprehend the causes of things, their precursors and their antecedents, so to speak; to compare similarities and to link and combine future with present events; and by seeing with ease the whole course of life to prepare whatever is necessary for living it.” Cicero, On Duties I. 11. eds. and trans. M.T. Griffin and E.M. Atkins (Cambridge 1991), p. 6. [Emphasis added]
According to Cicero, how does reason differentiate human beings from other animals? Humans share in reason that gives them the ability to perceive, comprehend and compare the interrelated nature of past, present, and future events. Thereby, reasonable human beings prepare for living.