When people were arguing about slavery.

The problem is, what to do when someone's actions are hurting or killing someone else.  

We have laws against hurting or killing someone else.  

When we kill a fetus, are we killing someone else?

It all comes down to whether or not a fetus is a human being.

Pro-lifers believe that yes, a fetus is a human being.

Fetus = latin for 'little one'.

When does the creation of a human being occur?

During the gestation?  Or at conception?

What is the definition of a human being?

*From thefreedictionary.com:  A human being is defined as 'a member of the genus Homo and especially of the species H. sapiens.'*

How do we determine a creature's genus and species?  
  
*Genetically.  (my answer)*

When are these genes present in an embryo?

*At conception - the very act of parental genes coming together to start a new life.  (my answer)*

Answers to these questions are hugely important. Historically we have seen how redefining what a human being has been used to kill, enslave, disenfranchise, and otherwise refuse rights to a group of people.  What are the rights Americans are entitled to?  Life, liberty, and the pursuit of happiness.  If some of us are entitled to those rights, all of us are.