Are fetuses "human beings"? Biological versus psychological definitions

Are fetuses human beings?

Many people believe that if they are, then abortion is generally wrong. 

But what is a human being? What do you mean "human being"? 

There are two broad answers or definitions of "human being":

1. Human beings are biologically human organisms. 
2. Human beings are biologically human organisms who are conscious and feeling, with knowledge and emotions and other cognitive, emotional, and social characteristics. 

About definition 2:

• people who deny that early fetuses are "human beings" generally have something like definition 2 in mind. (Ask them!).
• biologically human organisms who have psychological characteristics such as being conscious and feeling, with knowledge and emotions and other cognitive, emotional, and social characteristics are usually wrong to kill;
• but, fetuses are not "human beings" on this meaning of the term (which is better expressed as "human person"), and so the rule against killing human beings in this sense of the term does not apply to them. 

About definition 1:

• people who claim that fetuses are human beings generally have something like definition 1 in mind. And they are correct: (human) fetuses are, obviously, biologically human organisms;
• however, that would make abortion wrong only if a premise like this is true:

All biologically human organisms are typically wrong to kill. 

Is a premise or assumption like this true? Why would someone think it's true? 

Although many people assume that this is true, one can see why it's actually probably false by thinking about why human beings are wrong to kill. Human beings can't be wrong to kill just because they are human beings: there has to be more of an explanation: what are better explanations and maybe the best explanation? 

Thinking through these questions (and better answers arguably appeal to consciousness, sentient, feeling or awareness) contribute to reasons to think that this premise is not true: while many human organisms are wrong to kill, not all human organisms are like that, and early fetuses are among that "not all." 

This is just a start of this discussion and these issues are discussed here in this section of Thinking Critically About Abortion and these blog posts:

• When does human life begin? Would around 70% of people deny that "human life begins at conception"?
• On Saying What You Mean: the "Principle of Charity" and the "Principle of Clarity"
• "When does life begin? Biological versus Biographical Life"
• "Fetuses are human beings; all human beings are equal in dignity & worth; so abortion is wrong." Good or bad argument? 
• "When does life begin?' and 'Are fetuses human?': Two bad questions to ask about abortion."
• "Is your opinion on abortion wrong? Critical thinking and abortion."

All other blog posts are available here.