- The opposite of same / alike is different
- If two things have the same features then those two things are alike
- Hence, if two things have different features then those two things are different

- If two things have different features then those two things are different
- If things can be identified as different because of something then they are distinguishable by that something
- Hence, things are distinguishable by their features

- A mammal is a kind of animal
- A bird is a kind of animal
- Hence, a bird and a mammal are both kinds of animals

- A bird and a mammal are both kinds of animals
- An animal is a kind of living thing
- Therefore, a bird and a mammal are both kinds of things

- Things are distinguishable by their features
- A bird and a mammal are both kinds of things
- Hence, mammals and birds are distinguishable by their features

- A bird is a kind of object
- A mammal is a kind of object
- Hence, a mammal is a kind of object and a bird is a kind of object

- A mammal is a kind of object and a bird is a kind of object
- The parts of an object are features of that object
- Hence, the parts of a mammal / bird are features of the mammal / bird

- Feathers are a part of a bird
- Fur is usually part of a mammal
- Therefore, fur is a part of mammals and feathers are a part of birds

- The parts of a mammal / bird are features of the mammal / bird
- Fur is a part of mammals and feathers are a part of birds
- Therefore, fur is a feature of mammals and feathers are a feature of birds

- Mammals and birds are distinguishable by their features
- Fur is a feature of mammals and feathers are a feature of birds
- Hence, fur can be used to distinguish mammals from birds

Hence, fur can be used to distinguish mammals from birds
What do all mammals have in common that distinguishes them from birds?
- An animal is a kind of living thing 
- A bird is a kind of animal 
- If two things have the same features then those two things are alike 
- If things can be identified as different because of something then they are distinguishable by that something 
- A bird is a kind of object 
- The parts of an object are features of that object 
- Feathers are a part of a bird 
- A mammal is a kind of object 
- Fur is usually part of a mammal 
- A mammal is a kind of animal 
- The opposite of same / alike is different