diff --git a/src/Engine.cs b/src/Engine.cs
index 1d15bee..9c1de66 100644
--- a/src/Engine.cs
+++ b/src/Engine.cs
@@ -6,9 +6,9 @@ namespace Encompass
 {
     public abstract class Engine
     {
-        public readonly List<Type> mutateComponentTypes = new List<Type>();
-        public readonly List<Type> emitMessageTypes = new List<Type>();
-        public readonly List<Type> readMessageTypes = new List<Type>();
+        private readonly List<Type> mutateComponentTypes = new List<Type>();
+        private readonly List<Type> emitMessageTypes = new List<Type>();
+        private readonly List<Type> readMessageTypes = new List<Type>();
 
         private EntityManager entityManager;
         private ComponentManager componentManager;
diff --git a/src/World.cs b/src/World.cs
index a33e08e..b084162 100644
--- a/src/World.cs
+++ b/src/World.cs
@@ -4,19 +4,19 @@ namespace Encompass
 {
     public class World
     {
-        private List<Engine> engines;
+        private List<Engine> enginesInOrder;
         private EntityManager entityManager;
         private ComponentManager componentManager;
         private MessageManager messageManager;
 
         internal World(
-            List<Engine> engines,
+            List<Engine> enginesInOrder,
             EntityManager entityManager,
             ComponentManager componentManager,
             MessageManager messageManager
         )
         {
-            this.engines = engines;
+            this.enginesInOrder = enginesInOrder;
             this.entityManager = entityManager;
             this.componentManager = componentManager;
             this.messageManager = messageManager;
@@ -24,7 +24,7 @@ namespace Encompass
 
         public void Update(float dt)
         {
-            foreach (var engine in engines)
+            foreach (var engine in enginesInOrder)
             {
                 engine.Update(dt);
             }
diff --git a/src/WorldBuilder.cs b/src/WorldBuilder.cs
index c32f8c1..9e54821 100644
--- a/src/WorldBuilder.cs
+++ b/src/WorldBuilder.cs
@@ -1,15 +1,22 @@
+using System;
 using System.Collections.Generic;
+using System.Reflection;
+using System.Linq;
 
 namespace Encompass
 {
     public class WorldBuilder
     {
         private List<Engine> engines = new List<Engine>();
+        private DirectedGraph<Engine> engineGraph = new DirectedGraph<Engine>();
 
         private ComponentManager componentManager;
         private EntityManager entityManager;
         private MessageManager messageManager;
 
+        private Dictionary<Type, HashSet<Engine>> messageTypeToEmitters = new Dictionary<Type, HashSet<Engine>>();
+        private Dictionary<Type, HashSet<Engine>> messageTypeToReaders = new Dictionary<Type, HashSet<Engine>>();
+
         public WorldBuilder()
         {
             componentManager = new ComponentManager();
@@ -32,13 +39,122 @@ namespace Encompass
 
             engines.Add(engine);
 
+            engineGraph.AddVertex(engine);
+
+            var emitMessageAttribute = engine.GetType().GetCustomAttribute<Emits>(false);
+            if (emitMessageAttribute != null)
+            {
+                foreach (var emitMessageType in engine.GetType().GetCustomAttribute<Emits>(false).emitMessageTypes)
+                {
+                    if (!messageTypeToEmitters.ContainsKey(emitMessageType))
+                    {
+                        messageTypeToEmitters.Add(emitMessageType, new HashSet<Engine>());
+                    }
+
+                    messageTypeToEmitters[emitMessageType].Add(engine);
+
+                    if (messageTypeToReaders.ContainsKey(emitMessageType))
+                    {
+                        foreach (var reader in messageTypeToReaders[emitMessageType])
+                        {
+                            engineGraph.AddEdge(engine, reader);
+                        }
+                    }
+                }
+            }
+
+            var readMessageAttribute = engine.GetType().GetCustomAttribute<Reads>(false);
+            if (readMessageAttribute != null)
+            {
+                foreach (var readMessageType in engine.GetType().GetCustomAttribute<Reads>(false).readMessageTypes)
+                {
+                    if (!messageTypeToReaders.ContainsKey(readMessageType))
+                    {
+                        messageTypeToReaders.Add(readMessageType, new HashSet<Engine>());
+                    }
+
+                    messageTypeToReaders[readMessageType].Add(engine);
+
+                    if (messageTypeToEmitters.ContainsKey(readMessageType))
+                    {
+                        foreach (var emitter in messageTypeToEmitters[readMessageType])
+                        {
+                            engineGraph.AddEdge(emitter, engine);
+                        }
+                    }
+                }
+            }
+
             return engine;
         }
 
         public World Build()
         {
+            if (engineGraph.Cyclic())
+            {
+                var cycles = engineGraph.SimpleCycles();
+                var errorString = "Cycle(s) found in Engines: ";
+                foreach (var cycle in cycles)
+                {
+                    errorString += "\n" +
+                    string.Join(" - > ", cycle.Select((engine) => engine.GetType().Name)) +
+                    " -> " +
+                    cycle.First().GetType().Name;
+                }
+                throw new EngineCycleException(errorString);
+            }
+
+            var mutatedComponentTypes = new HashSet<Type>();
+            var duplicateMutations = new List<Type>();
+            var componentToEngines = new Dictionary<Type, List<Engine>>();
+
+            foreach (var engine in engines)
+            {
+                var mutateAttribute = engine.GetType().GetCustomAttribute<Mutates>(false);
+                if (mutateAttribute != null)
+                {
+                    foreach (var mutateComponentType in engine.GetType().GetCustomAttribute<Mutates>(false).mutateComponentTypes)
+                    {
+                        if (mutatedComponentTypes.Contains(mutateComponentType))
+                        {
+                            duplicateMutations.Add(mutateComponentType);
+                        }
+                        else
+                        {
+                            mutatedComponentTypes.Add(mutateComponentType);
+                        }
+
+                        if (!componentToEngines.ContainsKey(mutateComponentType))
+                        {
+                            componentToEngines[mutateComponentType] = new List<Engine>();
+                        }
+
+                        componentToEngines[mutateComponentType].Add(engine);
+                    }
+                }
+            }
+
+            if (duplicateMutations.Count > 0)
+            {
+                var errorString = "Multiple Engines mutate the same Component: ";
+                foreach (var componentType in duplicateMutations)
+                {
+                    errorString += "\n" +
+                    componentType.Name + " mutated by: " +
+                    string.Join(", ", componentToEngines[componentType].Select((engine) => engine.GetType().Name));
+                }
+
+                throw new EngineMutationConflictException(errorString);
+            }
+
+            var engineOrder = new List<Engine>();
+            foreach (var engine in engineGraph.TopologicalSort())
+            {
+                engineOrder.Add(engine);
+            }
+
             var world = new World(
-                this.engines,
+                engineOrder,
                 this.entityManager,
                 this.componentManager,
                 this.messageManager
diff --git a/src/encompass-cs.csproj b/src/encompass-cs.csproj
index f199fa6..d107759 100644
--- a/src/encompass-cs.csproj
+++ b/src/encompass-cs.csproj
@@ -21,5 +21,8 @@
     <Content Include="attributes\Emits.cs" />
     <Content Include="exceptions\IllegalMessageEmitException.cs" />
     <Content Include="exceptions\IllegalMessageReadException.cs" />
+    <Content Include="exceptions\EngineCycleException.cs" />
+    <Content Include="exceptions\EngineMutationConflictException.cs" />
+    <Content Include="attributes\Reads.cs" />
   </ItemGroup>
 </Project>
\ No newline at end of file
diff --git a/src/exceptions/EngineCycleException.cs b/src/exceptions/EngineCycleException.cs
new file mode 100644
index 0000000..2849787
--- /dev/null
+++ b/src/exceptions/EngineCycleException.cs
@@ -0,0 +1,13 @@
+
+using System;
+
+namespace Encompass
+{
+    public class EngineCycleException : Exception
+    {
+        public EngineCycleException(
+            string format,
+            params object[] args
+        ) : base(string.Format(format, args)) { }
+    }
+}
diff --git a/src/exceptions/EngineMutationConflictException.cs b/src/exceptions/EngineMutationConflictException.cs
new file mode 100644
index 0000000..d6cf4d7
--- /dev/null
+++ b/src/exceptions/EngineMutationConflictException.cs
@@ -0,0 +1,12 @@
+using System;
+
+namespace Encompass
+{
+    public class EngineMutationConflictException : Exception
+    {
+        public EngineMutationConflictException(
+            string format,
+            params object[] args
+        ) : base(string.Format(format, args)) { }
+    }
+}
diff --git a/src/graph/DirectedGraph.cs b/src/graph/DirectedGraph.cs
index 77d89a2..1eaaff2 100644
--- a/src/graph/DirectedGraph.cs
+++ b/src/graph/DirectedGraph.cs
@@ -159,6 +159,11 @@ namespace Encompass
             return output;
         }
 
+        public bool Cyclic()
+        {
+            return StronglyConnectedComponents().Any((scc) => scc.Count() > 1);
+        }
+
         public IEnumerable<T> TopologicalSort()
         {
             var dfs = NodeDFS();
diff --git a/test/DirectedGraphTest.cs b/test/DirectedGraphTest.cs
index f38cb66..2a3731e 100644
--- a/test/DirectedGraphTest.cs
+++ b/test/DirectedGraphTest.cs
@@ -341,5 +341,34 @@ namespace Tests
             result.Should().ContainEquivalentOf(cycleE);
             result.Should().HaveCount(5);
         }
+
+        [Test]
+        public void Cyclic()
+        {
+            var myGraph = new DirectedGraph<int>();
+            myGraph.AddVertices(1, 2, 3, 4);
+            myGraph.AddEdges(
+                Tuple.Create(1, 2),
+                Tuple.Create(2, 3),
+                Tuple.Create(3, 1),
+                Tuple.Create(3, 4)
+            );
+
+            Assert.That(myGraph.Cyclic(), Is.True);
+        }
+
+        [Test]
+        public void Acyclic()
+        {
+            var myGraph = new DirectedGraph<int>();
+            myGraph.AddVertices(1, 2, 3, 4);
+            myGraph.AddEdges(
+                Tuple.Create(1, 2),
+                Tuple.Create(2, 3),
+                Tuple.Create(3, 4)
+            );
+
+            Assert.That(myGraph.Cyclic(), Is.False);
+        }
     }
 }
diff --git a/test/WorldBuilderTest.cs b/test/WorldBuilderTest.cs
new file mode 100644
index 0000000..29093eb
--- /dev/null
+++ b/test/WorldBuilderTest.cs
@@ -0,0 +1,212 @@
+using NUnit.Framework;
+
+using Encompass;
+using System.Collections.Generic;
+
+namespace Tests
+{
+    public class WorldBuilderTest
+    {
+        public class EngineCycleSimple
+        {
+            struct AMessage : IMessage { }
+            struct BMessage : IMessage { }
+
+            [Reads(typeof(AMessage))]
+            [Emits(typeof(BMessage))]
+            class AEngine : Engine
+            {
+                public override void Update(float dt)
+                {
+                    BMessage message;
+                    this.EmitMessage(message);
+                }
+            }
+
+            [Reads(typeof(BMessage))]
+            [Emits(typeof(AMessage))]
+            class BEngine : Engine
+            {
+                public override void Update(float dt)
+                {
+                    AMessage message;
+                    this.EmitMessage(message);
+                }
+            }
+
+            [Test]
+            public void EngineCycle()
+            {
+                var worldBuilder = new WorldBuilder();
+                worldBuilder.AddEngine<AEngine>();
+                worldBuilder.AddEngine<BEngine>();
+
+                Assert.Throws<EngineCycleException>(() => worldBuilder.Build());
+            }
+        }
+
+        public class EngineCycleComplex
+        {
+            struct AMessage : IMessage { }
+            struct BMessage : IMessage { }
+            struct CMessage : IMessage { }
+            struct DMessage : IMessage { }
+
+            [Reads(typeof(AMessage))]
+            [Emits(typeof(BMessage))]
+            class AEngine : Engine
+            {
+                public override void Update(float dt)
+                {
+                    BMessage message;
+                    this.EmitMessage(message);
+                }
+            }
+
+            [Reads(typeof(BMessage))]
+            [Emits(typeof(CMessage))]
+            class BEngine : Engine
+            {
+                public override void Update(float dt)
+                {
+                    CMessage message;
+                    this.EmitMessage(message);
+                }
+            }
+
+            [Reads(typeof(CMessage))]
+            [Emits(typeof(DMessage))]
+            class CEngine : Engine
+            {
+                public override void Update(float dt)
+                {
+                    DMessage message;
+                    this.EmitMessage(message);
+                }
+            }
+
+            [Reads(typeof(DMessage))]
+            [Emits(typeof(AMessage))]
+            class DEngine : Engine
+            {
+                public override void Update(float dt)
+                {
+                    AMessage message;
+                    this.EmitMessage(message);
+                }
+            }
+
+            [Test]
+            public void EngineCycle()
+            {
+                var worldBuilder = new WorldBuilder();
+                worldBuilder.AddEngine<AEngine>();
+                worldBuilder.AddEngine<BEngine>();
+                worldBuilder.AddEngine<CEngine>();
+                worldBuilder.AddEngine<DEngine>();
+
+                Assert.Throws<EngineCycleException>(() => worldBuilder.Build());
+            }
+        }
+
+        public class MutationConflict
+        {
+            struct AComponent : IComponent { }
+
+            [Mutates(typeof(AComponent))]
+            class AEngine : Engine
+            {
+                public override void Update(float dt) { }
+            }
+
+            [Mutates(typeof(AComponent))]
+            class BEngine : Engine
+            {
+                public override void Update(float dt) { }
+            }
+
+            [Test]
+            public void MutationConflictException()
+            {
+                var worldBuilder = new WorldBuilder();
+                worldBuilder.AddEngine<AEngine>();
+                worldBuilder.AddEngine<BEngine>();
+
+                Assert.Throws<EngineMutationConflictException>(() => worldBuilder.Build());
+            }
+        }
+
+        public class LegalEngines
+        {
+            static List<Engine> order = new List<Engine>();
+
+            struct AComponent : IComponent { }
+            struct BComponent : IComponent { }
+
+            struct AMessage : IMessage { }
+            struct BMessage : IMessage { }
+            struct CMessage : IMessage { }
+            struct DMessage : IMessage { }
+
+            [Mutates(typeof(AComponent))]
+            [Emits(typeof(AMessage))]
+            class AEngine : Engine
+            {
+                public override void Update(float dt)
+                {
+                    order.Add(this);
+                }
+            }
+
+            [Mutates(typeof(BComponent))]
+            [Emits(typeof(BMessage))]
+            class BEngine : Engine
+            {
+                public override void Update(float dt)
+                {
+                    order.Add(this);
+                }
+            }
+
+            [Reads(typeof(AMessage), typeof(BMessage))]
+            [Emits(typeof(DMessage))]
+            class CEngine : Engine
+            {
+                public override void Update(float dt)
+                {
+                    order.Add(this);
+                }
+            }
+
+            [Reads(typeof(DMessage))]
+            class DEngine : Engine
+            {
+                public override void Update(float dt)
+                {
+                    order.Add(this);
+                }
+            }
+
+            [Test]
+            public void EngineOrder()
+            {
+                var worldBuilder = new WorldBuilder();
+
+                var engineA = worldBuilder.AddEngine<AEngine>();
+                var engineB = worldBuilder.AddEngine<BEngine>();
+                var engineC = worldBuilder.AddEngine<CEngine>();
+                var engineD = worldBuilder.AddEngine<DEngine>();
+
+                Assert.DoesNotThrow(() => worldBuilder.Build());
+
+                var world = worldBuilder.Build();
+
+                world.Update(0.01f);
+
+                Assert.That(order.IndexOf(engineA), Is.LessThan(order.IndexOf(engineC)));
+                Assert.That(order.IndexOf(engineB), Is.LessThan(order.IndexOf(engineC)));
+                Assert.That(order.IndexOf(engineC), Is.LessThan(order.IndexOf(engineD)));
+            }
+        }
+    }
+}
diff --git a/test/test.csproj b/test/test.csproj
index e69bcea..a294604 100644
--- a/test/test.csproj
+++ b/test/test.csproj
@@ -15,5 +15,6 @@
     <ProjectReference Include="..\src\encompass-cs.csproj" />
     <Content Include="EngineTest.cs" />
     <Content Include="DirectedGraphTest.cs" />
+    <Content Include="WorldBuilderTest.cs" />
   </ItemGroup>
 </Project>
\ No newline at end of file