diff --git a/dust-lang/src/abstract_tree.rs b/dust-lang/src/abstract_tree.rs
new file mode 100644
index 0000000..c9e35c9
--- /dev/null
+++ b/dust-lang/src/abstract_tree.rs
@@ -0,0 +1,28 @@
+use crate::{Identifier, Span, Value};
+
+#[derive(Debug, PartialEq, Clone)]
+pub struct Node {
+    pub operation: Statement,
+    pub span: Span,
+}
+
+impl Node {
+    pub fn new(operation: Statement, span: Span) -> Self {
+        Self { operation, span }
+    }
+}
+
+#[derive(Debug, PartialEq, Clone)]
+pub enum Statement {
+    // Top-level statements
+    Assign(Box<(Node, Node)>),
+
+    // Expressions
+    Add(Box<(Node, Node)>),
+    List(Vec<Node>),
+    Multiply(Box<(Node, Node)>),
+
+    // Hard-coded values
+    Constant(Value),
+    Identifier(Identifier),
+}
diff --git a/dust-lang/src/analyzer.rs b/dust-lang/src/analyzer.rs
new file mode 100644
index 0000000..26d1659
--- /dev/null
+++ b/dust-lang/src/analyzer.rs
@@ -0,0 +1,85 @@
+use crate::{Node, Span, Statement};
+
+pub struct Analyzer {
+    abstract_tree: Vec<Node>,
+}
+
+impl Analyzer {
+    pub fn new(abstract_tree: Vec<Node>) -> Self {
+        Analyzer { abstract_tree }
+    }
+
+    pub fn analyze(&self) -> Result<(), AnalyzerError> {
+        for node in &self.abstract_tree {
+            self.analyze_node(node)?;
+        }
+
+        Ok(())
+    }
+
+    fn analyze_node(&self, node: &Node) -> Result<(), AnalyzerError> {
+        match &node.operation {
+            Statement::Add(instructions) => {
+                self.analyze_node(&instructions.0)?;
+                self.analyze_node(&instructions.1)?;
+            }
+            Statement::Assign(instructions) => {
+                if let Statement::Identifier(_) = &instructions.0.operation {
+                    // Identifier
+                } else {
+                    return Err(AnalyzerError::ExpectedIdentifier {
+                        actual: instructions.0.clone(),
+                    });
+                }
+
+                self.analyze_node(&instructions.0)?;
+                self.analyze_node(&instructions.1)?;
+            }
+            Statement::Constant(_) => {}
+            Statement::Identifier(_) => {}
+            Statement::List(instructions) => {
+                for instruction in instructions {
+                    self.analyze_node(instruction)?;
+                }
+            }
+            Statement::Multiply(instructions) => {
+                self.analyze_node(&instructions.0)?;
+                self.analyze_node(&instructions.1)?;
+            }
+        }
+
+        Ok(())
+    }
+}
+
+#[derive(Clone, Debug, PartialEq)]
+pub enum AnalyzerError {
+    ExpectedIdentifier { actual: Node },
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::Value;
+
+    use super::*;
+
+    #[test]
+    fn analyze() {
+        let abstract_tree = vec![Node::new(
+            Statement::Assign(Box::new((
+                Node::new(Statement::Constant(Value::integer(1)), (0, 1)),
+                Node::new(Statement::Constant(Value::integer(2)), (1, 2)),
+            ))),
+            (0, 1),
+        )];
+
+        let analyzer = Analyzer::new(abstract_tree);
+
+        assert_eq!(
+            analyzer.analyze(),
+            Err(AnalyzerError::ExpectedIdentifier {
+                actual: Node::new(Statement::Constant(Value::integer(1)), (0, 1))
+            })
+        )
+    }
+}
diff --git a/dust-lang/src/instruction.rs b/dust-lang/src/instruction.rs
deleted file mode 100644
index bb683f6..0000000
--- a/dust-lang/src/instruction.rs
+++ /dev/null
@@ -1,23 +0,0 @@
-use crate::{Identifier, Span, Value};
-
-#[derive(Debug, PartialEq, Clone)]
-pub struct Instruction {
-    pub operation: Operation,
-    pub span: Span,
-}
-
-impl Instruction {
-    pub fn new(operation: Operation, span: Span) -> Self {
-        Self { operation, span }
-    }
-}
-
-#[derive(Debug, PartialEq, Clone)]
-pub enum Operation {
-    Add(Box<(Instruction, Instruction)>),
-    Assign(Box<(Instruction, Instruction)>),
-    Constant(Value),
-    Identifier(Identifier),
-    List(Vec<Instruction>),
-    Multiply(Box<(Instruction, Instruction)>),
-}
diff --git a/dust-lang/src/lib.rs b/dust-lang/src/lib.rs
index 06a69a3..62796ba 100644
--- a/dust-lang/src/lib.rs
+++ b/dust-lang/src/lib.rs
@@ -7,8 +7,9 @@ The [interpreter] module contains the `Interpreter` struct, which is used to lex
 interpret Dust code. The `interpret` function is a convenience function that creates a new
 `Interpreter` and runs the given source code.
 */
+pub mod abstract_tree;
+pub mod analyzer;
 pub mod identifier;
-pub mod instruction;
 pub mod lex;
 pub mod parse;
 pub mod token;
@@ -16,8 +17,9 @@ pub mod r#type;
 pub mod value;
 pub mod vm;
 
+pub use abstract_tree::{Node, Statement};
+pub use analyzer::Analyzer;
 pub use identifier::Identifier;
-pub use instruction::{Instruction, Operation};
 pub use lex::{lex, LexError, Lexer};
 pub use parse::{parse, ParseError, Parser};
 pub use r#type::Type;
diff --git a/dust-lang/src/parse.rs b/dust-lang/src/parse.rs
index 37ec5a1..286f75f 100644
--- a/dust-lang/src/parse.rs
+++ b/dust-lang/src/parse.rs
@@ -1,9 +1,9 @@
 use crate::{
     lex::{LexError, Lexer},
-    Instruction, Operation, Span, Token, Value,
+    Node, Span, Statement, Token, Value,
 };
 
-pub fn parse(input: &str) -> Result<Vec<Instruction>, ParseError> {
+pub fn parse(input: &str) -> Result<Vec<Node>, ParseError> {
     let lexer = Lexer::new(input);
     let mut parser = Parser::new(lexer);
     let mut instructions = Vec::new();
@@ -34,7 +34,7 @@ impl<'src> Parser<'src> {
         Parser { lexer, current }
     }
 
-    pub fn parse(&mut self) -> Result<Instruction, ParseError> {
+    pub fn parse(&mut self) -> Result<Node, ParseError> {
         self.parse_instruction(0)
     }
 
@@ -44,7 +44,7 @@ impl<'src> Parser<'src> {
         Ok(())
     }
 
-    fn parse_instruction(&mut self, precedence: u8) -> Result<Instruction, ParseError> {
+    fn parse_instruction(&mut self, precedence: u8) -> Result<Node, ParseError> {
         let left_instruction = self.parse_primary()?;
         let left_start = left_instruction.span.0;
 
@@ -56,8 +56,8 @@ impl<'src> Parser<'src> {
                     let right_instruction = self.parse_instruction(self.current_precedence())?;
                     let right_end = right_instruction.span.1;
 
-                    return Ok(Instruction::new(
-                        Operation::Add(Box::new((left_instruction, right_instruction))),
+                    return Ok(Node::new(
+                        Statement::Add(Box::new((left_instruction, right_instruction))),
                         (left_start, right_end),
                     ));
                 }
@@ -67,8 +67,8 @@ impl<'src> Parser<'src> {
                     let right_instruction = self.parse_instruction(self.current_precedence())?;
                     let right_end = right_instruction.span.1;
 
-                    return Ok(Instruction::new(
-                        Operation::Multiply(Box::new((left_instruction, right_instruction))),
+                    return Ok(Node::new(
+                        Statement::Multiply(Box::new((left_instruction, right_instruction))),
                         (left_start, right_end),
                     ));
                 }
@@ -78,8 +78,8 @@ impl<'src> Parser<'src> {
                     let right_instruction = self.parse_instruction(self.current_precedence())?;
                     let right_end = right_instruction.span.1;
 
-                    return Ok(Instruction::new(
-                        Operation::Assign(Box::new((left_instruction, right_instruction))),
+                    return Ok(Node::new(
+                        Statement::Assign(Box::new((left_instruction, right_instruction))),
                         (left_start, right_end),
                     ));
                 }
@@ -90,28 +90,22 @@ impl<'src> Parser<'src> {
         Ok(left_instruction)
     }
 
-    fn parse_primary(&mut self) -> Result<Instruction, ParseError> {
+    fn parse_primary(&mut self) -> Result<Node, ParseError> {
         match self.current.clone() {
             (Token::Float(float), span) => {
                 self.next_token()?;
 
-                Ok(Instruction::new(
-                    Operation::Constant(Value::float(float)),
-                    span,
-                ))
+                Ok(Node::new(Statement::Constant(Value::float(float)), span))
             }
             (Token::Integer(int), span) => {
                 self.next_token()?;
 
-                Ok(Instruction::new(
-                    Operation::Constant(Value::integer(int)),
-                    span,
-                ))
+                Ok(Node::new(Statement::Constant(Value::integer(int)), span))
             }
             (Token::Identifier(identifier), span) => {
                 self.next_token()?;
 
-                Ok(Instruction::new(Operation::Identifier(identifier), span))
+                Ok(Node::new(Statement::Identifier(identifier), span))
             }
             (Token::LeftParenthesis, left_span) => {
                 self.next_token()?;
@@ -121,7 +115,7 @@ impl<'src> Parser<'src> {
                 if let (Token::RightParenthesis, right_span) = self.current {
                     self.next_token()?;
 
-                    Ok(Instruction::new(
+                    Ok(Node::new(
                         instruction.operation,
                         (left_span.0, right_span.1),
                     ))
@@ -141,8 +135,8 @@ impl<'src> Parser<'src> {
                     if let (Token::RightSquareBrace, right_span) = self.current {
                         self.next_token()?;
 
-                        return Ok(Instruction::new(
-                            Operation::List(instructions),
+                        return Ok(Node::new(
+                            Statement::List(instructions),
                             (left_span.0, right_span.1),
                         ));
                     }
@@ -203,29 +197,23 @@ mod tests {
 
         assert_eq!(
             parse(input),
-            Ok(vec![Instruction::new(
-                Operation::List(vec![
-                    Instruction::new(Operation::Constant(Value::integer(1)), (1, 2)),
-                    Instruction::new(
-                        Operation::Add(Box::new((
-                            Instruction::new(Operation::Constant(Value::integer(1)), (4, 5)),
-                            Instruction::new(Operation::Constant(Value::integer(1)), (8, 9)),
+            Ok(vec![Node::new(
+                Statement::List(vec![
+                    Node::new(Statement::Constant(Value::integer(1)), (1, 2)),
+                    Node::new(
+                        Statement::Add(Box::new((
+                            Node::new(Statement::Constant(Value::integer(1)), (4, 5)),
+                            Node::new(Statement::Constant(Value::integer(1)), (8, 9)),
                         ))),
                         (4, 9)
                     ),
-                    Instruction::new(
-                        Operation::Add(Box::new((
-                            Instruction::new(Operation::Constant(Value::integer(2)), (11, 12)),
-                            Instruction::new(
-                                Operation::Multiply(Box::new((
-                                    Instruction::new(
-                                        Operation::Constant(Value::integer(4)),
-                                        (16, 17)
-                                    ),
-                                    Instruction::new(
-                                        Operation::Constant(Value::integer(10)),
-                                        (20, 22)
-                                    ),
+                    Node::new(
+                        Statement::Add(Box::new((
+                            Node::new(Statement::Constant(Value::integer(2)), (11, 12)),
+                            Node::new(
+                                Statement::Multiply(Box::new((
+                                    Node::new(Statement::Constant(Value::integer(4)), (16, 17)),
+                                    Node::new(Statement::Constant(Value::integer(10)), (20, 22)),
                                 ))),
                                 (15, 23)
                             ),
@@ -244,10 +232,10 @@ mod tests {
 
         assert_eq!(
             parse(input),
-            Ok(vec![Instruction::new(
-                Operation::List(vec![
-                    Instruction::new(Operation::Constant(Value::integer(1)), (1, 2)),
-                    Instruction::new(Operation::Constant(Value::integer(2)), (4, 5)),
+            Ok(vec![Node::new(
+                Statement::List(vec![
+                    Node::new(Statement::Constant(Value::integer(1)), (1, 2)),
+                    Node::new(Statement::Constant(Value::integer(2)), (4, 5)),
                 ]),
                 (0, 6)
             )])
@@ -260,7 +248,7 @@ mod tests {
 
         assert_eq!(
             parse(input),
-            Ok(vec![Instruction::new(Operation::List(vec![]), (0, 2))])
+            Ok(vec![Node::new(Statement::List(vec![]), (0, 2))])
         );
     }
 
@@ -270,8 +258,8 @@ mod tests {
 
         assert_eq!(
             parse(input),
-            Ok(vec![Instruction::new(
-                Operation::Constant(Value::float(42.0)),
+            Ok(vec![Node::new(
+                Statement::Constant(Value::float(42.0)),
                 (0, 4)
             )])
         );
@@ -283,10 +271,10 @@ mod tests {
 
         assert_eq!(
             parse(input),
-            Ok(vec![Instruction::new(
-                Operation::Add(Box::new((
-                    Instruction::new(Operation::Constant(Value::integer(1)), (0, 1)),
-                    Instruction::new(Operation::Constant(Value::integer(2)), (4, 5)),
+            Ok(vec![Node::new(
+                Statement::Add(Box::new((
+                    Node::new(Statement::Constant(Value::integer(1)), (0, 1)),
+                    Node::new(Statement::Constant(Value::integer(2)), (4, 5)),
                 ))),
                 (0, 5)
             )])
@@ -299,10 +287,10 @@ mod tests {
 
         assert_eq!(
             parse(input),
-            Ok(vec![Instruction::new(
-                Operation::Multiply(Box::new((
-                    Instruction::new(Operation::Constant(Value::integer(1)), (0, 1)),
-                    Instruction::new(Operation::Constant(Value::integer(2)), (4, 5)),
+            Ok(vec![Node::new(
+                Statement::Multiply(Box::new((
+                    Node::new(Statement::Constant(Value::integer(1)), (0, 1)),
+                    Node::new(Statement::Constant(Value::integer(2)), (4, 5)),
                 ))),
                 (0, 5)
             )])
@@ -315,13 +303,13 @@ mod tests {
 
         assert_eq!(
             parse(input),
-            Ok(vec![Instruction::new(
-                Operation::Add(Box::new((
-                    Instruction::new(Operation::Constant(Value::integer(1)), (0, 1)),
-                    Instruction::new(
-                        Operation::Multiply(Box::new((
-                            Instruction::new(Operation::Constant(Value::integer(2)), (4, 5)),
-                            Instruction::new(Operation::Constant(Value::integer(3)), (8, 9)),
+            Ok(vec![Node::new(
+                Statement::Add(Box::new((
+                    Node::new(Statement::Constant(Value::integer(1)), (0, 1)),
+                    Node::new(
+                        Statement::Multiply(Box::new((
+                            Node::new(Statement::Constant(Value::integer(2)), (4, 5)),
+                            Node::new(Statement::Constant(Value::integer(3)), (8, 9)),
                         ))),
                         (4, 9)
                     ),
@@ -337,22 +325,16 @@ mod tests {
 
         assert_eq!(
             parse(input),
-            Ok(vec![Instruction::new(
-                Operation::Assign(Box::new((
-                    Instruction::new(Operation::Identifier(Identifier::new("a")), (0, 1)),
-                    Instruction::new(
-                        Operation::Add(Box::new((
-                            Instruction::new(Operation::Constant(Value::integer(1)), (4, 5)),
-                            Instruction::new(
-                                Operation::Multiply(Box::new((
-                                    Instruction::new(
-                                        Operation::Constant(Value::integer(2)),
-                                        (8, 9)
-                                    ),
-                                    Instruction::new(
-                                        Operation::Constant(Value::integer(3)),
-                                        (12, 13)
-                                    ),
+            Ok(vec![Node::new(
+                Statement::Assign(Box::new((
+                    Node::new(Statement::Identifier(Identifier::new("a")), (0, 1)),
+                    Node::new(
+                        Statement::Add(Box::new((
+                            Node::new(Statement::Constant(Value::integer(1)), (4, 5)),
+                            Node::new(
+                                Statement::Multiply(Box::new((
+                                    Node::new(Statement::Constant(Value::integer(2)), (8, 9)),
+                                    Node::new(Statement::Constant(Value::integer(3)), (12, 13)),
                                 ))),
                                 (8, 13)
                             ),
diff --git a/dust-lang/src/vm.rs b/dust-lang/src/vm.rs
index b0c9acc..73d182f 100644
--- a/dust-lang/src/vm.rs
+++ b/dust-lang/src/vm.rs
@@ -1,4 +1,4 @@
-use crate::{parse, Instruction, Operation, ParseError, Parser, Value, ValueError};
+use crate::{parse, Node, ParseError, Parser, Statement, Value, ValueError};
 
 pub fn run(input: &str) -> Result<Option<Value>, VmError> {
     let instructions = parse(input)?;
@@ -8,11 +8,11 @@ pub fn run(input: &str) -> Result<Option<Value>, VmError> {
 }
 
 pub struct Vm {
-    instructions: Vec<Instruction>,
+    instructions: Vec<Node>,
 }
 
 impl Vm {
-    pub fn new(instructions: Vec<Instruction>) -> Self {
+    pub fn new(instructions: Vec<Node>) -> Self {
         Vm { instructions }
     }
 
@@ -26,9 +26,9 @@ impl Vm {
         Ok(previous_value)
     }
 
-    fn run_instruction(&self, instruction: &Instruction) -> Result<Option<Value>, VmError> {
+    fn run_instruction(&self, instruction: &Node) -> Result<Option<Value>, VmError> {
         match &instruction.operation {
-            Operation::Add(instructions) => {
+            Statement::Add(instructions) => {
                 let left = if let Some(value) = self.run_instruction(&instructions.0)? {
                     value
                 } else {
@@ -43,19 +43,19 @@ impl Vm {
 
                 Ok(Some(sum))
             }
-            Operation::Assign(_) => todo!(),
-            Operation::Constant(value) => Ok(Some(value.clone())),
-            Operation::Identifier(_) => todo!(),
-            Operation::List(_) => todo!(),
-            Operation::Multiply(_) => todo!(),
+            Statement::Assign(_) => todo!(),
+            Statement::Constant(value) => Ok(Some(value.clone())),
+            Statement::Identifier(_) => todo!(),
+            Statement::List(_) => todo!(),
+            Statement::Multiply(_) => todo!(),
         }
     }
 }
 
 #[derive(Clone, Debug, PartialEq)]
 pub enum VmError {
-    ExpectedValue(Operation),
-    InvalidOperation(Operation),
+    ExpectedValue(Statement),
+    InvalidOperation(Statement),
     ParseError(ParseError),
     ValueError(ValueError),
 }
@@ -82,4 +82,11 @@ mod tests {
 
         assert_eq!(run(input), Ok(Some(Value::integer(3))));
     }
+
+    #[test]
+    fn add_multiple() {
+        let input = "(a + b = 1)";
+
+        assert_eq!(run(input), Ok(Some(Value::integer(6))));
+    }
 }